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DAVISON'S

MAMMALIAN ANATOMY

WITH SPECIAL REFERENCE TO

THE CAT

STROMSTEN

MAMMALIAN ANATOMY

WITH SPECIAL REFERENCE TO

THE CAT

ALVIN DAVISON, Ph. D.

EX-FELLOW OF PRINCETON' UN'IVERSITY; PROFESSOR OF BIOLOGV
IN' LAFAYETTE COLLEGE

FOURTH EDITION. REVISED BY

FRANK A. STROMSTEN, D. Sc. (Princeton)

ASSOCIATE PROFESSOR OF ANIMAL BIOLOGY
STATE UNIVERSITY OF IOWA

WITH 123 ILLUSTRATIONS, MOST OF WHICH

WERE MADE BY W. H. REESE, A. M., FROM

THE AUTHOR'S DISSECTIONS

'Study nature, not books."

— Agassiz.

PHILADELPHIA

P. BLAKISTON'S SON & CO.

1012 WALNUT STREET

PRINTED IN U. S. A.
BY THE MAPLE PRESS COMPANY, YORK, PA,

PREFACE TO THE FOURTH ED

In the present edition certain additions have been made and
the sections on the muscular and vascular systems rewritten
and considerably enlarged. In the section on the muscles
Reighard and Jennings has been followed rather closely, but
the entire group of muscles with exception of a very few belong-
ing to the reproductive organs and the ear have been worked
over in class and by private dissections during the progress of
revision. In addition to Reighard and Jennings, reference has
also been frequently made to Hyman's ''Laboratory Manual
for Comparative Vertebrate Anatomy;" Wilder and Gage's
"Anatomical Technology;" William's edition of Straus-Dur-
cheim's plates; Kingsley's "Comparative Anatomy;" Bensley's
"Anatomy of the Rabbit;" Cunningham's "Human Anatomy;"
Wilder's "Mammalian Anatomy;" Jayne's "Mammalian
Anatomy; The Skeleton of the Cat;" Eycleshymer's "Anatomi-
cal Names;" and numerous journals.

A number of new drawings have been made for this edition,
five of which depict the muscles of the hind limbs — these, with
those already in the book, show more muscles than the average
student is likely to dissect. Other new pictures illustrate
the development of the vascular system. These have been
redrawn for the most part from the original papers to which
credit is given. The conventional figures of Boas showing the
phylogeny of the aortic arches are from Kingsley's Comparative
Anatomy. Huntington and McClure's colored figures showing
the development of the postcava have been so well reproduced
in black and white by Miss Hyman that they have been bor-
rowed and the figure showing the composite diagram of embryonic
veins of the cat has been redrawn to correspond with Hyman's
figures. The figure showing the adult venous system has been

Vi PREFACE TO THE FOURTH EDITION

drawn from photographs taken from actual dissections by
the writer. One specimen had a persistent jugular lymph sac
and this has been added to the figure to show its position and
venous tap. Certain other variations are shown also. The
writer will be glad to receive communications regarding varia-
tions in any of the systems as well as criticisms and suggestions.
The aim has been to make the text as concise as possible and
to keep to the present convenient size of the book as nearly
as possible. The index has been very much enlarged to make
it more useful.

Frank A. Stromsten.

CONTENTS

Page

Introduction i

The Biological Sciences i

Phylogeny and Classification of Vertebrates 2

Preparation and Preservation of Material 9

General Structure of a Vertebrate 17

The Skin and Its Appendages 25

The Skeleton 28

General Terms Used in Description of Bones 28

Tabulation of Bones 29

Structure of Bone 31

Bones of the Head 33

Vertebral Column 53

Sternum 61

Ribs 61

Thoracic Limb 63

Pelvic Limb 74

The Joints 83

The Muscles 87

Organs ant) Digestion 127

Alimentary Canal 127

Viscera i34

Accessory Glands of Digestion i43

Peritoneum i45

The Vascular System 150

Heart 150

Arteries of Trunk i54

Arteries of Xeck and Head i57

Arteries of Thoracic Limb 160

Arteries of Pelvic Limb 162

Venous System 165

Development of Vascular System 171

Development of Heart 172

Development of Aortic Arches 1 74

Development of Venous System i77

Lymphatic System 182

Development of Lymphatic System 187

Ductless Glands 188

Respiratory System 191

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Vlll CONTENTS

Page

Excretory and Reproductive Systems 198

Glands of the Skin 198

Urinary Organs 198

Female Organs of Reproduction 200

Male Organs of Reproduction 203

Nervous System 209

Brain 209

External Features 210

Internal Structure 214

Spinal Cord 225

Peripheral Nerves 231

Cranial Nerves 231

Spinal Nerves 233

Sympathetic System 240

Organs of Sense. 244

Cutaneous 244

Olfactory 245

Gustatory 245

Visual 246

Auditory 249

Glossary 256

Index 266

LIST OF ILLUSTRATIONS

Fig. Page

1. Injecting Syringe lo

2. Diagrammatic View of Operation for Injection ii

3. Method of Making Incision in the Carotid Artery for Injection 11

4. Method of Inserting the Cannula into a Vessel 12

5. Palmar Aspect of Cat's Paw with Cannual Inserted 12

6. Squamous Epithelial Cells •■ 17

7. Stratified Epithelium 17

8. Involuntary Muscle 18

9. Heart Muscle 20

10. Cartilage 21

11. Fibers of Voluntary Muscle 22

12. Fibers of Connective Tissue 23

13. Longitudinal Section of the Humerus of a Kitten 30

14. Longitudinal Section of the Femur 30

15. Cross-section of Bone 32

16. Diagram of the Bones of the Mammalian Skull Viewed Laterally 39

17. Dorsal Aspect of the Cat's Skull 40

18. Ventral Aspect of the Skull with the Left Auditory Bulla Removed. . . 44

19. Cut Surface of a Sagitally Bisected Skull 47

20. Medial or Inner Aspect of the Mandible So

21. Ventral Aspect of Larynx, Hyoid Bones, and Tongue 51

22. Lateral Aspect of the Skeleton 54

23. Plan of a Vertebra 56

24. Dorsocaudal Aspect of Atlas 56

25. Lateral Aspect of the Epistropheus 57

26. Latero-caudal Aspect of a Thoracic Vertebra 57

27. Caudal Aspect of Fourth Lumbar Vertebra 59

28. Dorsal Aspect of the Sacrum 59

29. Ventral Aspect of the Bones of the Thorax 60

30. Caudal Aspect of Sixth Rib 62

31. Lateral Aspect of the Scapula 64

32. Caudal Aspect of the Clavicle 64

;^;^. Cranial Aspect of the Humerus 65

34. Lateral Aspect of the Ulna 66

35. Medial Aspect of the Radius 67

36. Genealogy of the Horse 68-69

37A. Dorsal Aspect of Cat's Manus 70

37B. Generalized Type of Carpus 70

38. Lateral Aspect of Forelimb of Equus 71

39. Lateral Aspect of Coxal Bone 75

40. Ventral Aspect of Innominate Bones. , 75

X LIST OF ILLUSTRATIONS

Fig. Page

41. Caudal Aspect of Femur 77

42. Cranial Aspect of Tibia 77

43. Medial Aspect of Fibula 79

44. Dorsal Aspect of Hind-foot 80

45. Diagram of a Diarthrodial Joint 85

46. Lateral Aspect of Dissected Knee-joint 84

47. Caudal Aspect of Knee-joint 85

48. Ventral Aspect of Trunk and Neck Muscles 91

49. Medial or Inner Aspect of Hind Limb 99

50. Lateral View of Hind Limb 100

51. Lateral aspect of Upper Part of Hind Limb loi

52. Muscles of Dorsal Side of Hind Foot. , 106

53. Muscles of Sole of Foot 106

54. Lateral Aspect of the Muscles of the Cat 116

55. Lateral Aspect of the Muscles of the Thoracic Limb 118

56. Medial Aspect of the Muscles of Thoracic Limb 120

57. Ventral Aspect of the Muscles of Trunk and Thigh 123

58. Lateral Aspect of the Muscles of the Leg 123

59. Caudal Aspect of the Muscles of Crus and Foot 125

60. Diagram of a Gland 125

61. Diagram of the Chief Organs of the Cat 127

62. Dorsal Aspect of the Tongue and Larynx 128

63. Longitudinal Section of the Canine Tooth 130

64. Lateral Aspect of the Permanent Dentition 131

65. Viscera of the Human Body 135

66. Ventral Aspect of the Alimentary Canal 137

67. Transverse Section of the Cat 138

68. Cross-section of the Cardiac End of the Stomach 138

69. Gastric Glands 139

70. Cross-section of the Small Intestine 140

7 1 A. Villi and Glands of Intestine 140

71B. Lacteals and Portal System of Dog 141

72. Salivary Glands i43

73. Diagram of the Stomach of a Ruminant 147

74. Photograph of the Human Heart 151

75. Heart Viewed Ventrally 151

76. Heart Viewed Ventrally with Caudal Third Cut Off 152

77. Heart Viewed Dorsally 152

78. Chief Arteries of the Trunk i55

79. Ventral Aspect of the Arteries of the Head and Neck 158

80. Arteries of the Forelimb 161

81. Arteries of the Leg 163

82. Cross-section of Artery and Vein 166

83. Vein with Valves 167

84. Chief Arteries of Cat 169

85A. Arterial System of a Rabbit 170

LIST OF ILLUSTRATIONS XI

Fig. Page

85B. Arterial System of a Man 1 70

86a, b, c. Development of Heart 172-173

87. Development of Aortic Arches i75

88. Modifications of Aortic Arches in Vertebrates 176

89. Development of Venous System 178

90. Composite Diagram of Embr^'onic Veins 180

91. Ventral Aspect of Chief Lymphatic Vessels of the Cat 185

92. Photograph of the Lymphatic Capillaries and Vessels of Cat's Ear 186

93. Diagrammatic Transverse Section of the Chest 192

94. Photograph of a Lung Corrosion of a Puma 193

95. Diagrammatic View of the Lung i95

96. Photograph of Human Heart and Lungs 196

97. Ventral Aspect of Female Urogenital System 199

98. Median Longitudinal Section of a Kidney 200

99. Diagram of Structure of Kidney 200

100. Section of Ovary 202

1 01. Ventral Aspect of Male Reproductive Organs 204

102. Spermatozoa 205

103. Dorsal Aspect of the Brain 211

104. Ventral Aspect of the Brain 213

105. Diagram of the Ventricles • . 215

106. Sagittal Section of the Brain 216

107. Dorsal Aspect of the Brain with the Cerebellum and Portion of Cere-

brum Removed 218

108. Cross-section of the Brain Caudad of the Optic Chiasm 220

109. Cross-section of the Brain through Anterior Commissure 222

no. Photomicrograph of Cross-section of Human Spinal Cord 226

111. Diagrammatic Section of Spinal Cord 227

112. Nerve-cell 228

113. Diagram of the Relation of Cells and Fibers in the Spinal Cord 229

1 14. Ventral Aspect of the Branchial Plexus 234

115. Ventral Aspect of the Nerves of the Pelvic Limb 238

116. Cranial Half of Sympathetic System 241

117. Caudal Half of Sympathetic System 242

118. Pacinian Corpuscle 245

1 19. Longitudinal Section of the Eye 247

120. Diagram of the Mammalian Ear 250

121. Section of the Cochlea of the Calf 251

122. Photograph of Human Brain -. 253

123. Brain of the Rabbit 254

ELEMENTS

MAMMALIAN ANATOMY

INTRODUCTION

Since this book is designed for the use not only of students
who have pursued the study of biology for some time, but also
for those making their first actual acquaintance with the sub-
ject, it may be well to call attention to the fact that any animal
or plant may be considered from several different standpoints.
A general study of structure and of the relations of the various
systems and organs is known as Anatomy. Histology concerns
itself with the cell and cell aggregates or tissues composing the
organs. These two sciences are included in Morphology, a term
which by many is made to include also Embryology or Ontogeny,
treating of the development of an organism from the egg, or its
vegetable homologue, to the period of assuming adult charac-
teristics. Since ontogeny deals not only with the growth of
structure but also the process of growth, it may likewise be in-
cluded under Physiology, a science which has for its province
the investigation of the functions of the organs and systems.
A special field of physiology having for its consideration the
operations, especially the conscious operations of the nervous
system, constitutes the science of Psychology.

The same species of animals are not found in all parts of the
world. The lion and tiger are found wild only in the old world,
while the opossum is confined to the new world. Again, many
species of animals whose fossil remains indicate their existence
on earth several millions of years ago, have at present no living

2 ELEMEiNTS OF MAMMALIAN ANATOMY

representatives. A consideration of this geographical and stra-
tigraphical location of organisms forms the science of Distribu-
tion. The science of Phylogeny seeks to discover the geological
ancestral history of an organism.

A casual glance shows at once striking similarities and differ-
ences between the common cat, the lion, and the tiger. All
have retractile claws, the same number and kind of teeth, and
the same number of toes. On the other hand, the resemblances
between these cat-like animals and the dogs are less marked,
while the differences are more striking. The cats and dogs
resemble each other more closely than either does a horse.
Horses, dogs, and cats have numerous characters in common
which are not present in birds. The recognition of such resem-
blances and differences furnishes a basis of classification, the
treatment of which forms the science of Taxonomy.

THE PHYLOGENY AND CLASSIFICATION OF

VERTEBRATES

Vertebrates have existed upon the earth for a very long time,
so long, indeed, that the time and manner of their origin is very
uncertain From what great group of invertebrates they were
derived can only be surmised from embryological and morpho-
logical data. The evidence from paleontology is very incom-
plete and unsatisfactory. Within the class of vertebrates,
however, the geological history is more certain. As a matter
of fact, the detail in which the phylogeny of such groups as
the horse j the camel> and the elephant can be reconstructed
from their fossil remains is indeed marvelous.

Geologic time has been conveniently divided into eras, pe-
riods, epochs, ages, etc. The following table has been inserted
for reference in connection with the geological history of the
vertebrate types. Certain dates have been assigned to the
several eras more as a reminder that the mind must think in
terms of millions of years than that they are even approxi-
mated correct.

INTRODUCTION

Era

Time

Period

Age

Animal life

8,000,000
years.

Quarter-
nary.

Holocene. Age of Man.

Pleistocene. Recent Mammals. Ice Age.

CSS

w
U

Tertiary.

Pliocene.
Miocene.

Oligocene.

Eocene.

Modern Mammals. Equus.
Earlier modern Mammals. Pro-
tohippus.

Beginning modern Mammals.
Mesohippus.

Ancestors of modern Mammals.
Hyracotherium.

u
o
o

80,000,000
years.

Cretaceous.

Jurassic.
Triassic,

Reptiles dominant, birds and

mammals.
Reptiles preeminent.
Reptiles abundant, Mammals first

appear.

IS]

130,000,000
years.

Permian.

Carboniferous.

Devonian.

Silurian.

Ordovician.

Cambrian.

Reptiles appear.

Amphibians dominant.

Age of Fishes.

Selachians and Ostracoderms.

Ostracoderms.

Invertebrates.

Proterozoic.

Archeozoic.

1 . The Invertebrate Stage

I. Invertebrata. — Animals with no skeletal axis and without
a central nervous system entirely dorsal of the alimentary
canal. Their earliest appearance in geologic time is not
known.

2. The Protochordal Stage

II. Protochordata. — Small marine forms having, during part
of their life at least, a rudimentary skeletal axis and other
features marking them as a connecting link between the

4 ELEMENTS OF MAMMALIAN ANATOMY

invertebrates and vertebrates. They must have been pres-
ent in the Cambrian and Precambrian seas several hundred
milHon years ago. They are represented in modern times
by the worm-like Balanoglossus, the Tunicates and Bran-
chiostoma ( Amphioxus) .
III. Vertebrata. Forms with a skeletal axis and dorsal nerve-
cord whose anterior end is dilated into a brain.

3. The Cyclostome Stage

(A) Cyclostomata. — Fish-like forms having a circular
mouth, no jaws present, no paired appendages, skele-
ton poorly developed. They make their appearance
in the early Ordovician. The modern representatives
are the lampreys and hagfishes.

4. The Selachian Stage

(B) Gnathostomata. — True jaws, well-developed skeleton,
and usually with paired appendages. Include all
vertebrates above the cyclostomes.

a Ichthyopsida (Anamnia): Fish-like forms that breathe, at least
while young, by gills; paired appendages, no amnion or allantois.

I. Pisces (Fish). — Breathe by gills; median and paired
fins, except where the latter are lost by degenera-
tion.

(a) Selachii. — True jaws present for the first time;
gill slits reduced in number; body covered with
plate-like (placoid) scales; notochord strength-
ened by blocks of cartilage; general organ sys-
tems foreshadowing those of the higher types.
A knowledge of the anatomy of selachians
is fundamental to a proper understanding of
the embryology and morphology of vertebrates
in general. Sharks swarmed the Silurian seas.
The modern representative of the selachians
are the sharks, rays and torpedoes.

INTRODUCTION c

5. The Ganoid Stage

(b) Ganoidei. — An ancient group of armored fishes
in which the skeleton becomes partly ossified;
air-bladder with a persistent open duct present
hydrostatic in function and foreshadowing the
lungs. Abundant in Devonian and Carbonifer-
ous times. Modern representatives are the
sturgeon and pike.

{d) Dipnoi.— Lung or mud-fishes; isolated surviv-
ors of a very ancient group of Devonian fishes.

6. The Amphibian Stage

2. Amphibia.— Legs instead of fins; lungs replacing
gills in adult. Mud tracks attributed to amphib-
ians have been found in the Devonian and early
carboniferous times but abundant fossils are first
found in the latter Carboniferous times. The earlier
forms were called stegocephalians on account of a
curious bony protection for the skull. One branch
which reached its highest development in the Per-
mian has been thought by some palaceontologists to
be the ancestor of mammals. Many forms reached
considerable size. The modern representatives are
frogs, toads and salamanders.

/3 Amniota: Amnion and allantois present; gills never func-
tional; fins never present.

7. The Reptilian Stage

3. Reptilia. — Whole body covered with scales or plates;
poikilothermic, i.e. body temperature more or less
changeable with surroundings. Although fossil
reptiles have not been found until toward the close
of the Paleozoic during the early part of the Per-

ELEMENTS OF MAMMALIAN ANATOMY

mian, they doubtless began to differentiate from the
stegocephalian amphibians much earlier. Their
development was so rapid in the Mesozoic times
that they dominated the earth, the sea and the sky.
They reached enormous proportions. One of the
terrestrial forms, a dinosaur, measured over 90 feet
in length; with head erect could reach to a height
of 30 feet, although its normal height was but 15
feet. The sea forms, or ichthyosaures, were also of
large size. They were fish-like in shape and were
frequently provided with long slender jaws armored
with sharp conical teeth. There were also flying
reptiles, Pterosaures, with a wing-spread of over 20
feet. Of the twenty-five or more Mesozoic orders,
but a few of the more insignificant types remain
to-day; such as snakes, turtles, lizards, crocodiles
and alligators.

Aves (Birds). — ''Warm-blooded" animals with
feathers: An offshoot of the reptiles.

8. The Mammalian Stage

, Mammalia. — Vertebrates suckling their young;
hairs never entirely absent; diaphragm complete;
heart four-chambered; aorta curved to the left; red
blood-cells, when fully formed, without a nucleus
and round, except in the camel where they are
elliptical. The advent of mammals occurs during
the triassic. They are probably related to the
reptiles through the theromorphs. The mammals
of the early Cenozoic were small and insignificant.
However, they soon become the dominant type of
animal, so that the Cenozoic becomes known as the
age of mammals. The secret of their success is
their four-chambered heart and their protective
covering of hair.

INTRODUCTION 7

(A) Prototheria.— Very primitive, egg-laying (oviparous)
mammals. Represented in modern times by the duck-
bill (Ornithorhynchus) and spiny ant-eater (Echidna)
of Australia. Upper Triassic to modern times.

(B) Eutheria.— Viviparous mammals with anus and uro-
genital openings distinct.

a Didelphia (JMarsupialia) : Pouched mammals. Typically carry-
mg the young in a pouch; placenta rudimentary or primitive.
Jurassic to modern. The modern r'epresentatives are the opos-
sums and kangaroos.

^ Monodelphia (Placentalia) : Young nourished before birth by a
placenta; never carried in pouch.

(A) Unguiculata.— Clawed placental mammals.
Mesozoic to modern. Adapted to terrestrial, fos-
sorial, arboreal, aquatic, cursorial, and volant life.

1. Insectivora.— (Moles, shrews, and hedgehogs.)
Eocene to modern.

2. Chiropkra.—{Bsits). Miocene to modern.

3. Carnivora. — Eocene to modern. Modern forms
under two suborders:

{a) Fissipedia. — Dogs, raccoons, bears, wea-
sels and the cats, hyenas, etc.
{b) Pinnipedia. — Seals, walruses, etc.
4- Rodentia. — Rabbits, squirrels, beavers, rats,
mice, and porcupines. Oligocene to modern.
5. Edentata.— 'Cloths, ant-eaters, and armadillos.
Miocene to modern.
(5) Primates.— Fingers terminating in ''nails" as
distinguished from mammals with claws (un-
guiculates) or hoofs (ungulates). Eocene to
modern. Adapted to arboreal and ambulatory
life. Lemuroids, lemurs, monkeys, apes and man.
Probably arose from shrew-like insectivores.
(C) Ungulata.— Hoofed mammals. Eocene to mod-
ern. The Condylarthra and other primitive and

8 ELEMENTS OF MAMMALIAN ANATOMY

extinct forms are omitted from this list. The
modern orders are as follows:

6. Arliodaclyla. — Even-toed ungulates (pigs,
camels, deer, sheep and oxen).

7. Pcrissodactyla. — Odd-toed ungulates (tapirs,
horses, and rhinoceroses).

8. Prohoscidea. — Mastodons and elephants.

9. Sirenia. — Aquatic modifications of the Un-
gulata (sea cows and dugongs).

10. Hydracoidea. — (Conies). Rock and tree-liv-
ing ungulates. Oligocene to present. Syria
and Africa.
(D) Cetacea. — Whales and Dolphins. Eocene to pres-
ent.

A glance at the above outline shows that the class Mammalia
is divided into two subclasses, Prototheria and Eutheria; the
latter of which include the Didelphia and the Monodelphia.
The Monodelphia, or placental mammals, includes four cohorts;
mammals with claws, mammals with nails, mammals with
hoofs, and aquatic mammals. The Cat belongs to the unguicu-
lates and to the order Carnivora, or flesh-eaters. There are
two suborders of modern carnivores, the Fissipedia, or terres-
trial forms, and the Pinnipedia, or aquatic forms. There are
eight families in the suborder Fissipedia, of which the Canidae
(dogs), Ursida? (bears), and Felidae (cats) are the most fre-
quently seen in America. The family Felidae is represented by
only two living genera, Cynaclurus and Felis. The genus Felis
includes several species, of which Felis leo (the lion) , Felis tigris
(the tiger), and Felis domestica (the cat) are the most familiar.
Of the last species, there are several varieties, such as Maltese,
Angora, and Manx cats.

Linnaeus, born in Sweden, 1707, invented the system of bi-
nomial nomenclature in accordance with which the scientific
name of every plant and animal is composed of two parts, the
generic and specific. Thus the house cat is designated Felis

INTRODUCTION 9

domestica; the lion, Felts leo; the dog, Canis fa miliar is; the wolf,
Cams lupus; the pig, Sus scrofa; the red deer, Cervus elephus;
the elephant, Elephas Africanns; the orang-outang, Simla saty-
rus; and man Homo sapiens.

METHODS OF PRESERVING MATERIAL

Alcohol has been widely used as a preservative, but owing
to the fact that it is expensive and quickly evaporates from
the specimen exposed to the air, thereby rendering the parts
dry and brittle, its use has been largely supplanted by formalin.
Formalin, CH^O, is often sold under the names of formose,
formol, formine, formalosa, and formaldehyd. It can be pur-
chased for about thirty cents a pound. For preserving any
animal or plant, the concentrated 40% formaldehyd is diluted
with water in the proportion of ninety-five parts of the latter to
five parts of the former. It is evident, therefore, that one pound
of formaldehyd will make about ten liters of preserving fluid.

The specimens may be kept a year or two without changing
the formalin in ordinary stone jars with covers, but for perma-
nent preservation the glass jar with the ground-glass cover
should be used.

Preparation of Vascular System. — To render the vessels
plainly visible and distinguish the arteries from the veins, it is
advisable to inject the former with a yellow or red mass and the
latter with a blue mass. These fluid masses should be of such a
character as to harden in a short time after injection, so that
they will not run out when the vessels are cut during dissection

A syringe of hard rubber, having a capacity of about two
ounces, serves very well for injection. A cannula of correct
size may be had by asking the druggist for the filling cannula
of the Parke Davis serum syringe. The end to be inserted into
the blood-vessel should be ground off obliquely and smoothly
on a whetstone. The connection between the cannula and
nozzle is formed by stiff rubber tubing which should be securely
tied to the cannula (Fig. i).

ELEMENTS OF MAMMALIAN ANATOMY

The injecting mass is prepared by thoroughly mixing loo c.c.
of water, 20 c.c. of glycerin, 20 c.c. of concentrated formalin,
and 85 gm. of common laundry starch. One-half should be
colored yellow by adding powdered chrome yellow and the
other colored blue by dissolving in it a gram
or two of soluble Berlin blue. These liquid
masses, after being passed through a fine
wire strainer or a coarse piece of cheese-cloth
stretched across a funnel, may be preserved
for any length of time in covered jars.

The animal may be anesthetized by plac-
ing it in a tight box and administering il-
luminating gas, ether or chloroform. If
only the arteries are to be infected, the cat
may remain in the box until dead; but if
the veins are also to be injected, it is pref-
erable to use illuminating gas for the
anesthetic and then remove the animal to
the tray as soon as it is unconscious, and
reflect a portion of skin, exposing the ex-
ternal jugular veins (Fig. 2). With the
curved forceps thrust beneath the vein a
cord may be pulled through and tied in a
loose knot. One-half inch from the latter
a second cord should be tied around the
vein loosely. An oblique cut (Fig. 3) with
Fig. I.— Injecting the point of the scissors directed caudad is
/>, Plunger handle; then made in the veins between the cords.

b, barrel; pi, nozzle; j^g incision should extend about half-way

c, cannula; r, rubber *

tube; dt, point of de- through the vcsscl. Absorbing the blood
tachment; s, string, ^^j^ absorbent cotton as it runs from the

vessel will prevent clogging. If too much ether has not
been used, the blood will continue running fifteen minutes.
When it has nearly ceased flowing the carotid artery must be
found by making a slit in the muscle alongside of the trachea

INTRODUCTION

just mediae! of the jugular, as indicated by the line d (Fig. 2).

Having cut through the muscle, two white cords are seen along

either side of the trachea. The

medial one may be red, as it is

the carotid artery. The lateral

one, lying in the same sheath

with the preceding, is the vagus

or tenth cranial nerve. Sepa-
rate the artery from the nerve

and tie two cords loosely

around the vessel as in the

case of the jugular. Lift up the

artery with the index finger

(Fig. 3), and make an oblique

incision with the scissors. The

cannula with the connecting tube

attached should then be inserted

caudad in the oblique cut of

the artery (Fig. 4), and the string

^ drawn tight so as to hold the

cannula in place. The string

st should then be tightened to

prevent the injection mass from running out where the cannula

is inserted. After stirring the red mass, filling the syringe, and

slipping the nozzle into the con-
necting tube the operator should
press slowly but continuously on
the plunger until that portion of
the carotid craniad of the string
st is well distended. In a large

Fig. 3.-METHOD OP Making ^^\ this will not OCCUr Until the

Incision IN THE Carotid Artery Syringe is nearly or quite empty.

NjECTioN. When the vessels are full, the

cannula is withdrawn while the string s is tightened. The

syringe is washed out, after which the blue mass is well stirred

Fig. 2. — Diagrammatic View of
Operation for Injection.
d. Broken line showing course of
the carotid artery beneath; h, string
loosely tied; c, transverse vein unit-
ing external jugulars; a, points of
curved forceps containing string.

ELEMENTS OF MAMMALIAN ANATOMY

and injected caudad into the external jugular in the same man-
ner as described for the arteries.

By making a slit about three inches long in the abdominal
wall, a fold of the intestine may be pulled
out so that its lumen can be filled with
about 200 c.c. of 15% formalin. The
same amount should be injected into
the lungs by inserting the cannula
caudad into the ventral wall of the
trachea. If the cat is not to be used at
once, it may be preserved indefinitely in
a jar of five per cent, formalin.

The portal system is not injected
through the jugular vein. The portal
trunk just caudad of where it enters the
Fig. 4.— Method of liver may be found by cutting a piece from

Inserting the Can- ., 1 1 • i n -i • i . .1

NULA into a Vessel, the abdommal wall on the right ventral

aspect just caudad of the last rib. After
two loose knots are tied around this trunk as directed for the
jugular, the cut is made and the cannula inserted into the
portal system of a large specimen. This
should not be injected until the other sys-
tems have been filled.

The lymphatic system must likewise be
injected for demonstration. While the cat
is being anesthetized, dilute India ink, or 5
gm. of soluble Berlin blue are dissolved in
100 gm. of water, and the solution warmed
to about the temperature of the body. As aspect of Cat's Paw
soon as the cat is unconscious the syringe ^^'"" Cannula In-

•^ " SERTED.

should be warmed by filling it with hot
water, and the point of the cannula pushed obliquely
proximad under the thick skin on the palm (Fig. 5) of
the paw. The syringe after being half filled with India ink or
Berlin blue solution is attached to the cannula and the plunger

Fig.

-Palmar

INTRODUCTION 1 3

pushed in very slowly so that one-fourth of the amount in the
syringe is forced out in ten minutes. While the injection is
being made the limb should be gently massaged by pinching
and rubbing from the foot toward the body. This facilitates
the flow of the liquid in the lymph-vessels. In this manner the
lymphatics of each limb are filled. The author has been able to
fill the left thoracic duct by continuing the injection for about
twenty minutes in the palm of the left paw. The lymphatics
of the head and neck may be injected in a similar manner by
inserting the cannula beneath the skin on the tip of the ear,
the top of the tongue, the tip of the nose, and the lips.

In order to inject the lacteals the abdominal cavity must be
opened, and the cannula inserted very obliquely into the wall
of the small intestine so that its point is between the mucous
and muscular coats. The half-filled syringe being attached,
very gentle pressure should then be exerted on the plunger,
until the injecting solution appears in the lacteals. To inject
all the lacteals it is necessary to insert the cannula into the wall
of the intestine at a dozen different places. To fill the thoracic
duct, injection may be made into the large lymphatic gland lying
at the point where the covering blood-vessels of the mesentery
meet. The best solution for injecting the thoracic duct is made
by dissolving 7 gm. of gelatin in a warm Berlin blue solution (4
gm. of Berlin blue to 100 c.c. water). This should be filtered
through a single layer of absorbent cotton and then injected,
while still quite warm. In all cases injections to fill the lym-
phatics must be warm and must be pushed in very slowly.
These lymphatic injections are best preserved by injecting
the trachea and intestine with 95% alcohol and immersing the
cat in a jar of 70% alcohol. Professor Gage makes a beautiful
demonstration of the lymphatic system by feeding — a cat that
has been starved 18 to 24 hours some butter colored — with
Sudan III. After three or four hours the cat is killed and dis-
sected. The lymphatics stand out in red.

14 KLEMEMS OF MAAlAl ALLAN ANATOMY

Preparation of a Mammal for Dissection of the Muscles,
Peripheral Nerves and Viscera. — The simplest method is to
anesthetize the animal as before described and then remove the
skin, taking great care to avoid cutting away the superficial
muscles. The cannula should be pushed through into the tra-
chea and ICO c.c. of 15% formalin injected to fill the lungs.
An equal amount of formalin should be injected into the
stomach through a glass tube pushed down the esophagus. The
same quantity of formalin should be injected at two or three dif-
ferent places into the intestines by making a median incision
into the abdominal wall and pulling out a loop of the intestine
into which the cannula may be thrust. The specimen is then
to be immersed in a jar of 5% formalin. A better method is to
inject into the carotid artery 200 c.c. of glycerinated formalin
(water 140 c.c, glycerin 30 c.c, formalin 30 c.c), and half that
amount into the intestine and trachea. The specimen may
then be preserved in 5% formalin.

Preparation of the Central Nervous System. — The animal
may be killed either with chloroform or ether. About 200 c.c
of formal-bichromate (170 c.c. of 5% potassium bichromate
and 30 c.c of formalin) are then injected slowly craniad into
the carotid artery (Figs. 2, 3, and 4). After skinning, the eyes
should be cut out and the flesh removed from the head and
dorsal side of the vertebral column. On a line connecting the
caudal borders of the orbits, cut through the skull to the brain
with the bone cutters and remove piece by piece the roof of the
skull. Next cut away the lateral walls down to the base of the
brain. Care must be exercised in laying bare the cerebellum,
and cutting loose the tentorium cerebelli, the plate of bone
separating the cerebrum from the cerebellum. The spinal
cord is next laid bare dorsally, beginning with the atlas, by
cutting through the pedicles of the neural arches on either side.
With a sharp knife or a pair of scissors the spinal nerves may
then be cut and the cord lifted from behind forward out of its
bed, until the brain is reached. The latter must be carefully

INTRODUCTION 1 5

raised while the nerves at its base are cut, and the dura mater
loosened.

The brain is firm enough to dissect as soon as removed, but
it is better to further harden it and differentiate the white and
gray matter by placing it in weak formal-bichromate (5%
formalin, 500 c.c. + 5% potassium bichromate, 500 c.c.)
one week in the dark. Light causes a precipitate. At the end
of one week the specimen should be placed in 1000 c.c. of 5%
formalin for another week, after which it is ready for dissection.
In case brains of calves or sheep are used a hammer and bone
chisel are necessary for opening the skull. The head should
first be nailed to the tray. As soon as the brain is removed it
should be placed in a large pan of water and the dura mater
carefully cut away, the clotted blood washed off and a syringe-
ful of strong formal-bichromate injected into the third ventricle
by pushing the cannula about an inch through the infun-
dibulum (Fig. 103). The brain of a sheep or calf will be very
soft when removed, as it cannot be hardened previously by
injecting the hardening fluid into the arteries. Therefore it is
necessary to lay the specimen on absorbent cotton in the jar
of formal-bichromate, which must be exchanged for fresh
fluid on the second and third days. At least two weeks are
required for hardening the brain of a sheep or calf, after
which it is placed in 5% formalin for a week or more to wash
out the bichromate before dissection. Brains are best pre-
served permanently in 85% alcohol. The brain of the cat
or sheep may be satisfactorily prepared for dissection by plac-
ing it immediately upon removal from the skull into a 5% solu-
tion of formaldehyd, where it may remain until needed.

Preparation of the Osseous System. — A mounted skeleton
of the cat may be purchased for about eight dollars. It is far
more satisfactory, however, to use the disarticulated bones for
study. These are easily prepared in the following manner:
As soon as the animal is dead, the skin and the greater part of
the flesh should be cut away and the internal organs removed.

1 6 ELEMENTS OF MAMMALIAN ANATOMY

The bones with much llcsh remaining on them are then put
into 7000 c.c. of water containing 150 grams of ''Gold Dust,"
or powdered soap. This may then be boiled from two to four
hours but better results are given by using the low flame and
keeping the solution at a temperature between 75 and go
degrees centigrade from 3 to 6 hours. As soon as the flesh falls
freely off the bones they should be brushed clean in a pan of
water and the brain broken to pieces with a bent wire thrust
into the foramen magnum. The contents of the skull may then
be washed out under the tap. This treatment renders the
bones perfectly clean, white and free from grease.

By heating the bones from one to two hours only and not
allowing the temperature to rise above 85 degrees, the flesh
may be brushed from the limbs without removing the ligaments
holding the bones together. When dry, the bones are held
firmly in their natural relations. In treating the skeletons of
kittens or those of smaller animals such as mice, birds and
frogs, only one half the amount of gold dust should be used and
a temperature between 70 and 80 degrees maintained.

GENERAL STRUCTURE

Fig, 6. — Detached
Squamous Cells from
THE Mouth. (Lewis and
Stohr.)

The study of any vertebrate reveals the presence of numer-
ous organs, each of which is for the performance of a particular
function. Thus the heart is the organ for the propulsion of
the blood, the kidney for the elimination
of the nitrogenous waste. Several organs
combined for a common purpose consti-
tute a system. The heart, with the various
vessels for conveying the blood, forms the
circulatory system. The following eight
systems are found in all Mammalia:
Osseous or bony, muscular, digestive,
respiratory, vascular, excretory, repro-
ductive, and nervous.

The relative locations of the various systems are represented

diagrammatically in Fig. 6i. The
organs have the same arrangement
throughout all the orders of mammals.
Moreover, the minute structure of the
same organ is so similar in the different
species that in many cases even the
microscope will not enable one to tell
from which of several kinds of mam-
mals the organ has been taken.

Organs are made up of simpler ele-
ments, the tissues. Tissues are formed
of cells and intercellular substance,
sometimes the one and sometimes the
Fig. 7.— Stratified other is more in evidence.

Epithelium from the

CEsopHAGus OF A Child. THc ccll has been called the struc-

ewts an to r.) tural Unit of the body. Typically,

it is a mass of living matter, protoplasm, containing a central

denser body, the nucleus. The nuclear substance is very

1 8 ELEMENTS OF MAMMALIAN ANATOMY

complex and is separated from the rest of the cell by a nu-
clear membrane which performs an important function in
general cell activity. The nucleus contains a highly organized
substance, the cJiromatin, which is important in reproduction
and metabolism and is supposed to be the bearer of hereditary
characters. During cell-division the chromatin material may
be collected in definite masses or rods, chromosomes, the num-
ber and appearance of which are constant for the species. The
animal cell has no definite cell wall but the peripheral layer of

protoplasm is so modified as to act like a
semipermeable membrane which plays, an
important role in cellular activity.

Cells vary in size, shape, structure and

arrangement according to function or

pressure. Cells differentiated to perform

a certain definite function are grouped

Fig. 8.— In\'oluntary together w^ith a certain amount of in-

MuscLE-cELLs. X 250. tcrccllular substance to form a tissue.

n. Nucleus of a cell.

There are four primary tissues: epithelial,
connective, rnusctdar, and nervous.

Epithelial tissues line all the inner and outer surfaces of
the body. They are distinguished by the importance of the
cells and the small amount of intercellular substance, cement.
They serve for protection, secretion, excretion, and reaction
to stimuli. They may be simple, that is made of a single row
of cells as in the intestine, or complex or stratified, made up of
several layers as in the skin. Epithelial cells form the paren-
chyma of all secreting glands.

Connective tissues are distinguished by the large amount of
intercellular substance. They form the supporting elements
of the body. Ordinary connective tissues are recognized by
the character of their fibers or their cells. Those recognized by
their fibers are white fibrous or tendon, yellow elastic, reticu-
lar, and areolar. The areolar is the commonest kind and is
found everywhere, as just beneath the skin, between muscle

GENERAL STRUCTURE I 9

bundles and elsewhere loosely joining structures together.
Reticular tissue forms binding tissue of many glands. These
recognized by their cells are fat or adipose tissue, pigmented
tissue, and lymphatic or adenoid tissue.

Skeletal connective tissues form the more rigid supporting
tissues of the body. They are of two kinds: cartilage and hone.
There are three kinds of cartilage, distinguished by the char-
acter of the intercellular substance or matrix.

Hyaline cartilage is characterized by its homogeneous matrix
in which the cells are imbedded singly or in groups of two or
more. It is the most abundant and is commonly known as
gristle. It forms the articular cartilage of long bones, the costal
cartilage of ribs, and the cartilages of the respiratory system.
The entire embryonic skeleton with exception of a few bones of
the skull was at first hyaline cartilage. White fihro cartilage
and yelloiv elastic cartilage are recognized by the presence of
white or yellow fibers as the name indicates and have a much
more limited distribution.

Bone is a much more compact firm tissue than cartilage and is
limited to the skeleton. The superficial layers of flat bones and
of the epiphysis and the main portion of the diaphysis or shaft
of long bones are composed of compact bone while the middle
layer of long flat bones and the larger portion of the epiphysis
of long bones is spongy or cancellous bone (Fig. 14). In the
epiphysis the plates of cancellous bone are arranged in curved
lines such as to give the greatest strength to the bone (Fig. 14).

Muscular tissues are of three types: striated, unstriated or
smooth and cardiac. The voluntary striated are the skeletal
muscles of the body. They are composed of long cylindrical
fibers or cells having a number of nuclei located peripherally just
beneath the cell membrane, or sarcolemma. The unit of struc-
ture is the myofibril or sarcostyle which is cross-striated and
gives the characteristic appearance to this type of muscle. The
number of myofibrillae in each cell or muscle fiber may be
very great. The involuntary or smooth muscle cell has no

20 ELEMENTS OF MAMMALIAN ANATOMY

sarcolcmma, the nucleus is central, and the shape is spindle-like
or the cells may be joined together to form a syncytium (Fig. 8).
The cardiac muscle is composed of broad branching fibers of
cells united into a syncytium. The nucleus is central and the
fibrils striated. A sarcolemma has been described surrounding
the cardiac libers (Fig. 9).

Nucleus. Sarcoplasm. Fibrils. Lateral branch.

X. Conn, tissue. Capillaries.

Fig. 9. — Longitudinal Section of a Papillary Muscle from the Human

Heart. X 240. {Lewis and Stohr.)
The transverse lines (x) are partly light (where the fiber has broken) and partly

dark (intercalated discs).

Nervous tissues are made up of two kinds of elements:
nerve cells and nerve fibers. Nerve cells vary much in size and
shape, but typically comprise cell body, a fiber-process or axone,
and a series of branching processes, the dendrites. The nerve
cell with all its processes is known as a neurone (Fig. 112). The
nerve fiber has as its axis or core the axone, which in most cases

GENERAL STRUCTURE

is enclosed in certain membranes or coats. Certain fibers of
the sympathetic nervous system are surrounded by a delicate
homogeneous membrane, the neurolemma, and are known as
nonmednllatcd fibers. The fibers of the central nervous system
are generally distinguished by an intermediate layer of myelin

'^^^^^s^^

•*< ,^-'

'*^v;i%'

-i-:^

v'S

ix*t:

^.^c:^*^'

:■<«»> .*if;

■■^>--^

J^iLj

,V,,^>Yg^:,j^

Fig. 10. — The Three Types of Cartilage: A, Hyaline; B, Elastic; C

Fibrous. (Radasch.)
a, b. Outer and inner layers of perichondrium;
older cartilage cells; e, f, capsule surrounded by
lacuna.

c, young cartilage cells; d,
deeply staining matrix; g.

between the axis cylinder and the neuolemma and are known as
medullated fibers. The myehn sheath is more or less interrupted
at regular intervals by the so-called nodes of Ranvier, Nerves
are bundles of nerve fibers arranged in a parallel fashion and
enveloped in a connective-tissue sheath or epineurium. Nerves
carrying impressions to the central nervous system are known as
afferent or sensory nerves; those carrying impulses peripherally
are the efferent or motor nerves.

2 2 ELEMENTS OF MAMMALIAN ANATOMY

The different relative arrangements of these anatomic ele-
ments together with their morphology, permit one to know
from what organ any particular section of tissue under con-
sideration has been taken.

Fig. II. — Photomicrograph of Fibers of Voluntary Muscle, X loo.
Note the finer threads of connective tissue.

These ultimate units of structure are still further resolved
into parts by the chemist, who has show^n that they are com-
posed largely of carbon, hydrogen, oxygen, and nitrogen.
Since there can be no energy developed in the body without
the breaking dow^n of the complex organic compounds stored
up by the cells or else by the destruction of the cells them-
selves, it is plain that they must have their losses replaced in

GENERAL STRUCTURE

order to continue their existence. Therefore a method of pre-
paring the food for the use of the cells, and a way of trans-
porting it to each of them are necessary.

The former is accomplished by the digestive system, which,
through the agency of the salivary, gastric, pancreatic, and
other glands, transforms the food into a special liquid state
capable of being absorbed by the millions of minute finger-like
villi of the small intestine (Fig. 71a). Thence it is transferred
by the lacteal vessels and veins to the heart, whence it is con-

FiG. 12. — Subcutaneous Tissue from a Cat. (Lewis and Stohr.)
The fiber a has been treated with dilute acetic acid; the other fibers have
been teased apart and examined, unstained, in water, a, c. White fibers; h,
fat cell; d, connective tissue cell; e, elastic fibers.

veyed by the arteries to their capillary distribution in the neigh-
borhood of every cell in the body.

The waste material resulting from the cell activity is of two
kinds, gaseous and liquid. These waste products diffuse
through the capillary walls into the blood or are carried through
the lymphatics to the veins. Carbon dioxid is carried to the
heart and thence by the pulmonary arteries to the lungs, where
it passes into the terminal branches of the trachea, and finally
by expiration reaches the exterior. The liquid excretion is
transported by means of the lymphatics, veins and arteries to
the kidneys, where it diffuses through the walls of the capillaries
into the minute tubules opening into the ureters leading to the

24 ELEMENTS OF MAMMALIAN ANATOMY

bladder. It must be remembered that the material known as
feces passed out of the alimentary canal through the anus is not
an excretion of the cells of the body, but largely that portion of
the food not transformed into a condition permitting it to be
absorbed by the villi.

In addition to these systems necessary for the maintenance
of life, the cat requires a means for supporting the body and
moving about, furnished by the osseous and muscular systems.
The osseous system serves not only for support and locomotion,
but also for the protection of the. delicate vital organs. The
skull and spinal column contain the brain and spinal cord, while
the heart and lungs are well shielded by the dorsal vertebrae,
the ribs, and sternum. Likewise the muscles ward off serious
injuries from the blood-vessels, as they cover to a considerable
depth nearly all large arteries, and also aid by their contraction
in moving the lymph through the numerous lymphatic vessels
extending from the extremities to the jugular veins.

These systems previously described are capable of per-
forming their functions only when supplied with nerves through
which impulses can be transmitted from the brain and spinal
cord.

The only system which is not absolutely necessary to the life
of the cat is the reproductive; but this is required for the con-
tinuance of the species. It is not, however, functional during
the entire life, but as a rule only from the end of the first to
the tenth year.

LABORATORY STUDIES AND SUGGESTIONS

1. What advantages are derived from the study of mammalian anatomy?

2. Define morphology and state a fact from that science.

3. What two sciences does biology include?

4. What five sciences are included in zoology?

5. Make a physiologic statement concerning the heart.

6. State five facts belonging to the science of distribution.

7. What is taxonomy?

8. Name five classes of vertebrates.

9. By examining specimens discover what external feature distinguishes a
reptile from an amphibian.

THE SKIN 25

10. Do all mammals have hair?

11. What habit is common to no other vertebrates except mammals?

12. Give two points of dilTerence between the two subclasses of Mammalia.

13. Name the orders of Eutheria and give an example of each.

14. Which orders derive their names from the habits of the animals?

15. Which orders derive their names from anatomic features?

16. Which orders are aquatic?

17. What is the ultimate syllable of all family names?

18. Explain what is meant by binomial nomenclature.

19. Name three families of Carnivora.

20. Examine specimens and determine where in the teeth of Canidae differ
from those of Felidae.

21. What two rank names constitute the scientific name of an animal?

22. Give the scientific name of five Carnivora, two Ungulata, and two
Primates.

23. Define organ, system, tissue, and cell.

24. Name two organs belonging to each system.

25. How do the elements of the four kinds of tissue differ?

THE SKIN AND ITS APPENDAGES

The skin invests the body completely and is continuous with
the lining of the digestive and urogenital canals. It varies in
thickness in different regions, being very thin on the lips, ears,
and eyelids, and exceedingly thick on the pads of the feet and
on the ventral neck region, where, in contest with an enemy,
it is most likely to be seized. A fibrous connective tissue binds
the skin to the subjacent structures. In some places the union
is very firm, as on the distal parts of the limbs and the head,
while in other regions it is loose, as on the lateral aspect of the
trunk.

The skin consists of an external layer, the epidermis, and
beneath this, the dermis or true skin, designated the corium.
The epidermis is composed of numerous strata of epithelial
cells. Those on or near the surface are much flattened while
the deeper ones are more or less cubical. As the superficial
layer desquamates in minute fragments, forming what is com-
monly called dandruff, it is replaced by cells developed from
the deeper layers.

26 ELEMENTS OF MAMMALIAN ANATOMY

At the orifices of the internal passages, such as the diges-
tive and genital tracts, the epithelium changes to a soft deli-
cate nature, and is then known throughout these passages as
mucous membrane.

The coriiim or dermis is a form of fibrous connective tissue
whose deepest portion forms the white fluffy areolar sub-
stance cut in remo\ing the skin. In many regions just below
the true skin is a layer of adipose tissue, which when examined
under the microscope is seen to be composed of numerous
globular fat-cells supported by fibrous areolar tissue. The
seven pads on the forepaw and the five on the hind one con-
sist of greatly thickened epidermis, the corium, and masses
of fibrous connective tissue enveloping many fat-cells.

The sebaceous or oil glands lie in the corium, and by means
of a duct open into the hair follicle near the surface. The
sudoriferous or sweat glands, composed of coiled tubes, are
present in the subcutaneous tissue, from whence a duct ex-
tends to the surface. Although there are no blood-vessels
in the epidermis, numerous nerve terminations are present
in the deeper portions. The true skin is richly supplied with
both nerves and blood-vessels.

The claws produced by a special modification of the epider-
mis are among the most important appendages of the skin.
Five of these are present on each forefoot, while only four
occur on the hind one. At the root of each claw, the dermis
forms a crescentic fold over it, and beneath is a number of
papilla? richly suppHed with blood-vessels. This entire struc-
ture forms the matrix of the claw, which is set around the
terminal part of the distal phalanx of each digit. Claws, or
sonle similar structures, such as nails or hoofs, are present in
all mammals except the Cetacea.

Another important appendage of the skin is the hair, which
covers the entire body except the tip of the nose and the pads
of the feet. Its length and color vary with the variety of the
cat. The Mombus cat of Africa has short stiff hair, while

THE SKIN 27

the Angora or Persian cat is remarkable for the length and
delicacy of its soft fur. The hair, like the nails, is an extreme
modification of the epidermis. Each hair grows from a papilla
at the bottom of a small sac, the follicle, which is a depression
in the corium. The central part of the hair is the pith, and
the external portion, formed of thin overlapping scales, the
cuticle. The coloring-matter lies in the cortex, and may be
disposed in such an irregular manner that one-half of a hair is
white, and the other half yellow.

The large hairs on either side of the nose are known as
vihrisscB. Their roots are provided with delicate nerve-endings
of touch, so that the animal may find its way with ease through
dark narrow passages. There are a few long hairs above the
eyes, forming the eyebrows, but no eyelashes are present.

Most of the hairs are inserted obliquely into the skin, but
when angered the cat can erect them by the contraction of a
small muscle passing from the skin to the hair-bulb.

On some mammals the hairy covering is partial and limited
to particular regions; in others, as the hippopotamus and the
Sirenia, it is very scanty, but scattered over the whole sur-
face; while in the Cetacea it is reduced to a few small bristles
about the mouth.

Some kinds of hair, as those of the mane and tail of the
horse, are shed and renewed annually. Most mammals have
a long hairy coat in winter which gives place in spring to a
short coat. The Arctic fox, hare, ermine, and numerous other
animals of the colder regions undergo a complete change of
color in the two seasons, being white in winter and brown or
gray in summer. By this protective coloration they escape
many of their enemies.

THE SKELETON

The number of bones in the skeleton of the cat varies with
its age, since two or more bones separate in the young may
form one mass in the old animal. The three portions of the in-
nominate bone which are distinct (Fig. 39) in the young,
become fused in the adult. In very old age many sutures of
the skull become partially or wholly obliterated. In the young
adult cat the number of bones, exclusive of the teeth, ear
bones, chevron bones, and sesamoid bones, is about 233. The
sacrum is reckoned as one bone, though composed of three
coalesced vertebrae. The structure and embryology of the
teeth show that they belong to a different category from the
bones. The ossicula auditus, or ear bones, are the malleus,
incus, and stapes of the middle ear. The chevron bones are
eight in number, attached to the ventral side of the vertebrae
of the tail. The sesamoid bones number about forty, of which
the patella, or knee-cap, is the largest. They are formed in the
tendons where there is much pressure or friction, as upon the
volar surface of the metacarpus. The outline on page 29 gives
the classification, names, and number of the different bones of
the skeleton.

GENERAL TERMS USED IN DESCRIPTION OF BONES

In reference to shape the bones are spoken of as long, short,
flat, and irregular. Long bones are those having a shaft or
diaphysis in which is a cavity filled with marrow, and two
enlarged extremities or epiphyses (Fig. 13) : femur, fibula, meta-
carpals, and phalanges. Short bones are those not elongated
and with no medullary cavity: tarsus and carpus. Flat bones
are plate-like, with a layer of cancellous tissue between two
layers of compact tissue: parietal, scapula, and innominate.
Irregular bones are those which have an exceedingly irregular

THE SKELETON

f Skull

Axial Skele-
ton

Head

Cranium

Face

Trunk

Appendicu-
lar Skele-
ton

Thoracic limb

Hyoid bones

Vertebral column

Thorax

Shoulder girdle

Arm

Forearm

Pelvic limb

Hand

Pelvic girdle

Carpus

Frontal 2

Ethmoid i

Temporal 2

Parietal " -2

Interparietal i

Occipital I

[ Sphenoid i

Premaxillary 2

Maxillary 2

Palatine 2

Vomer i

Maxilloturbinal 2

Nasal 2

Lachrymal 2

Malar or Jugal 2

Mandible i

Tympanohyal 2

Stylohyal 2

Epihyal 2

Ceratohyal 2

Basihyal i

Thyrohyal 2

Cervical vertebrae 7

Thoracic vertebrae i.l

Lumbar vertebrae 7

Sacral vertebrae i

Caudal 21

fRibs 26

\ Sternum i

/ Scapula 2

\ Clavicle 2

Humerus 2

/Ulna 2

\ Radius 2

Scapholunar 2

Triquetral 2

Pisiform 2

Greater multangular. . . 2

Lesser multangular 2

Capitate 2

Hamate 2

Leg

Metacarpus ^^

[ Proximal ^o

Phalanges -^ Middle 10

[Distal 8

Innominate 2

I Femur 2

Patella 2

Tibia 2

Fibula 2

Foot

Tarsus

Talus 2

Calcaneum 2

Scaphoid. 2

Internal cuneiform 2

Middle cuneiform 2

External cuneiform .... 2

Cuboid 2

Metatarsus 10

. Phalanges

Proximal 8

Middle 8

Distal 8

ELEMENTS OF MAMMALIAN ANATOMY

shape: ethmoid and vertebra. The aspect of a bone is the
portion seen when viewed from a given direction. The bor-
der of a bone is the margin, edge, or ridge at the juncture of
two surfaces. Proximal is used to designate the portion of a

Fig. 13. — Longitudinal Section
OF THE Humerus of a Kitten.
h. Epiphysis for head; c, cartilage;
h, bone; m, medullary substance; o,
epiphysis for olecranon process.

Fig. 14. — Longitudinal Section of
THE Femur.
md. Medullary cavity; d and h, can-
cellous tissue; tr, cancellous tissue of
trochanter process; h, compact bony
tissue.

structure nearer the axis or spinal column, in distinction to
distal, which signifies the part farther removed from the axis.
Cranial indicates the part of an organ nearer to the plane
passing just beyond the head and perpendicular to the spinal
axis, while caudal is applied to the other part of the organ
nearer to the perpendicular plane at the end of the extended
tail.

THE SKELETON 3 1

Sagittal refers to the plane bisecting the animal in a vertical
and longitudinal direction. Medial and lateral are adjectives,
the former meaning nearer to the sagittal plane and the latter
more remote on either side of that plane. Proximal, distad,
craniad, caudad, mediad and laterad are adverbs indicating direc-
tion in accordance with the adjectives to which they are
related.

A process is projection or elevation.

A tuberosity is a rough obtuse process.

A tubercle is a small and usually more or less pointed process.

A condyle is a rounded and somewhat elongated smooth
articular process. The distal end of the femur presents a
pair of condyles (Fig. 41).

A fossa is an irregular depressed area (Fig. 31).

A foramen is an aperture for the passage of vessels or nerves.

The shaft is the body or middle portion of an elongate bone.

The head is a spheroidal prominence at one end of an elon-
gated bone (Fig. 41).

The epiphysis is a small process of bone ossified from a
separated center. In the young animal it is attached to the
main bone by cartilage, but in the adult becomes a part of
the main bone (Fig. 13). The femur has four epiphyses, one
for the head, one for the distal extremity, and one for each
trochanter process (Fig. 41). With the exception of the pha-
langes, metacarpals, and metatarsals, all of the long bones
have an epiphyses at each extremity. In the human, these
epiphyses do not unite with the shaft before the sixteenth
year. Diploe is the spongy layer of bone between the compact
surface layer of the flat bones (Fig. 19).

The articulation of a bone has reference to its contact with
other bones by means of joints.

STRUCTURE OF BONE

Every bone is completely covered except on its articulating
surfaces with a tough membrane, the periosteum, which serves

3>^

ELEMENTS OF MAMMALIAN ANATOMY

for the attachment of muscles, and the renewal of bony tissue
in case of injury. The long bones contain a cavity, the medul-
lary cavity, filled with marrow (Fig. 13). This cavity is lined
with cndosicum, a membrane similar to the periosteum.

^id''')

V'-^

\ ^

- -"-y- ',

'^m-^m

if.Trrfag ja Lr^nt-Sibhr

Fig. 15. — Part of a Cross-section of a Decalcified Phalanx from an

Adult.

I, Resorption line; 2, Volkmann's canals; 3, periosteum; 4, periosteal lamellae;
5, perforating fibers; 6, Haversian lamella); 7, Haversian canal; 8, interstitial
lamellae; 9, endosteal lamellae; 10, marrow. (Lewis and Slohr.)

The shaft of the long bone is composed mainly of compact
bony tissue through which extend longitudinally intercom-
municating microscopic channels. Haversian canals, for the
conveyance of blood-vessels, nerves and lymphatics.

THE SKELETON ^^

The laciince, or spaces for the bone cells during life, are
arranged concentrically about the Haversian canals. The
canaliculi, or processes of the lacunar, communicate with one
another. At the extremities of the bones the place of the
medullary canal is taken up by cancellous tissue (Fig. 14, d),
the compact tissue being very thin. The flat bones have no
medullary canal, but the diploe or cancellous tissue lying
between the outer compact tissue has its spaces filled with a
red marrow of the same nature as that in the cancellous tissue
of the long bones, wherein the red blood-corpuscles are formed.
The large medullary cavity or canal is filled with yellow or
fatly marrow.

THE BONES OF THE HEAD

The Skull As a Whole. — The skull is the expanded cranial
portion of the axial skeleton. It encloses the brain and affords
protection and support for the organs of taste, smell, sight,
and hearing. In the adult state, it is a very complex struc-
ture. It differs from the rest of the skeleton in that, save for
the mandible and hyoidean apparatus, its several parts are so
tightly joined together by immovable joints {synarthrosis) that
it can be separated only with great difficulty. Some of the
bones are so completely fused together that the individual
parts can no longer be recognized. A skull in which the bones
have been separated is known as a disarticulated skull. A skull
may be disarticulated by filling it with dried beans and soaking
in water for some time.

When the skull of a cat is examined with respect to its
morphological structure it appears to be formed of three, or
including the olfactory capsule, four rings or segments. Each
of these rings is made up of a series of bones which enclose the
space occupied by the central nervous system. Older anato-
mists believed that they saw in these relations evidence for a
theory that the skull was formed by the fusion of four modified
vertebrae, each corresponding to one of these rings. This

34 ELEMENTS OF MAMMALIAN ANATOMY

theory is no longer held, being contrary to well-established
facts of comparative anatomy and embryology. Neverthe-
less a study of the make-up of these rings will be a convenient
way of introducing the names and locations of the bones of
the skull.

The most posterior or caudal of these rings may be called
the occipital segment. It consists of four bones completely
fused together to form a single bone. These are the hasiocci-
pilal, the two rxoccipituls, and the supriwccipital. Each of
these take part in forming the border of the foramen magnum,
although the exoccipitals have the greatest share.

Immediately anterior to the occipital ring is the parietal
segment. It is formed of five bones: the basis phenoid, two
alisphenoids, and two parictals. The occipital and parietal
segments are separated ventrolaterally by a hiatus into which
is wedged the auditory capsule.

The most anterior of the rings which form the wall of the
brain case proper is the frontal segment. It, too, consists of
five bones: the presphenoid, two orbitosphcnoids, and two fron-
lals. Like the occipital segment it is also separated ventro-
laterally from the parietal by an open space which in this case
is the orbital fissure, an exit for several nerves from the brain.

In addition to the three segments mentioned above, there
arc three sense capsules.

The olfactory capsule forms the most anterior of the cranial
segments and may be called the olfactory segment. It consists
of two tubular cavities open at each end. Each of these cavi-
ties is j^artially divided into an upper olfactory chamber, closed
behind by the cribriform plate; and a lower nasal chamber,
terminating in the choancc.

The inner wall of each cavity is formed mainly by the
mesethmoid and vomer. The outer wall is formed mainly by
the pterygoid, the palatine, the maxilla, the premaxilla, the
lachrymal, and a portion of the frontal. The roof is formed by
the nasal process or the frontal and the nasal. The horizontal

THE SKELETON 35

plates of the palatine, maxilla, and premaxilla form the floor
of the nasal cavity and as well, the hard palate or roof of the
mouth. The interior of the nasal cavity is occupied by the
ethmoid. A portion of the ethmoid sometimes forms j)art of
the inner wall of the orbit back of the lachrymal bone and is
known as the os planum.

The auditory capsule is enclosed in the temporal bone. The
temporal bone is formed by the fusion of the squam^ous, petrous,
and tympanic bones, which form, respectively, the squamous,
petrous, and tympanic portions of the bone.

The optic capsule is the largest and most conspicuous of
the sense capsules. With exception of the malar all bones
connected with it have already been noted.

It is thus seen that each of the three posterior cranial rings
is related to an important sense organ. The olfactory organ is
anterior to the frontal segment, the organ of sight lies between
the frontal and parietal, and the organ of hearing, between the
parietal and occipital segments.

These anatomical relations kept in mind will serve to orient
the several features of the complex bony skeleton of the head.
We shall now examine the skull from its several aspects.

As seen from the dorsal aspect (Fig. 17) the general outline
of the skull is oval. It presents a median somewhat ])ear-
shaped portion and the lateral expanded zygomatic arches. The
surface is smooth and unevenly convex in both directions. The
anterior half is flattened and triangular in shape. I'he pos-
terior half is very convex and circular. The antero-posterior
midline is marked by the sagittal suture, which divides the
surface into two symmetrical halves. The sagittal suture is
crossed transversely midway back by the fronto-parietal or
coronal suture. The postero-lateral angles of the anterior moiety
is projected outward and downward as the fronto-postorhital
processes. These approach similar projections from below and
form the posterior bony rim of the orbits. The orbit of the
cat is not entirely closed behind, differing in that respect from

^6 ELEMENTS OF MAMMALIAN ANATOMY

the condition found in the sheep, horse, and ox. On the other
hand, the orbit is less widely open in the cat than in the dog
and rabbit.

The posterior or caudal boundary of the dorsal surface is
sharply elevated into the lamhdoidal crest. The edge of the
lambdoidal crest becomes broadened at its central point into
a triangular or diamond-shaped area, the external occipital pro-
tuberance, which is continued forward on the interparietal bone
as the sagittal crest.

Viewed from the posterior aspect the general outline of the
skull, neglecting the zygomatic arches, is dome-shaped. The
posterior or nuchal surface, is somewhat triangular in shape
and is placed at right angles to the axial line of the cervical
vertebrae. The surface is roughened below the lambdoidal
crest for the attachment of several important muscles of the
head and neck. The lower portion is perforated by a large
opening, the foramen magnum occipitale, for the exit of the
central nervous system. On either side of the foramen mag-
num there is a smooth cylindrical projection, the occipital
condyle, for articulation with the atlas of the vertebral column.
Laterad and separated from the condyle by the deep jugular
fossa is the jugular process. Still laterad from this and sepa-
rated by a V-shaped notch is the mastoid process of the tem-
poral bone. The two processes cover most of the caudal and
caudo-lateral portions of the tympanic bulla. They also fur-
nish attachment for the digastric (depressor mandibular), stylo-
glossus, and stylomastoid muscles. The dorsal alanto -occipital
membrane is attached to the dorsal border of the foramen
magnum, between the condyles. The ventral alanto-occipital
membrane is attached to the ventral border of the foramen
magnum. These together with the articular capsules form the
capsular ligament between the occipital bone and the vertebral
column.

Viewed from the ventral aspect (Fig. i8) the skull presents a
somewhat oval outline. Its surface is flattened and is divided

THE SKELETON 37

by the orbits into an anterior triangular portion and a posterior
quadrilateral portion, joined medially by a trough-like isthmus
and laterally by the zygomatic arches. The anterior surface
or hard palate forms the floor of the nasal chamber and lies
on a lower level than the basicranium. The basicranium, or
posterior portion, comprises the basioccipital, basisphenoid,
and presphenoid bones. On each side of the basioccipital a
large, rounded tympanic bulla projects boldly below the general
level of the surface. The presphenoid is likewise flanked by
two downward projections, the lateral lamince of the pterygoids,
which are terminated ventro-caudally by the hamular proc-
esses. These lamina? form the walls of a deep median fossa
which, in life, is covered by soft palate and constitutes the
nasopharynx.

A number of foramina and depressions may be seen on the
ventral surface. The foramen magnum occipitale has already
been noted. The condyloid canal perforates the lateral margin
of the foramen magnum near the upper extremity of the con-
dyle. The hypoglossal foramen opens into the inner caudo-
medial margin of the jugular for a 7nen located at the caudomedial
angle of the tympanic bulla. The stylomastoid foramen and
the pit for the tympano-hyal at the caudolateral border of
the bulla. Craniad of these is the large external acoustic meatus.
In front of the bulla are the slit-like petrotympanic fissure, the
canal of Hugier, and the opening of the tuba auditiva or Eusta-
chian tube. On the lower surface of the zygomatic process of
the temporal bone is the mandibular fossa for the articulation
of the lower jaw. Mediad from this is the clearly defined
foramen ovale and in front of this on the margin of the orbit
is the somewhat smaller foramen rotundum. Above these is a
shallow groove, the lateral pterygoid fossa. Mediad of this is a
shorter, shallower groove, the scaphoid fossa, which passes
diagonally inward to within the lateral lamina of the ptery-
goid. Caudally the scaphoid fossa passes into the auditory
tube. Just within and anterior to the scaphoid fossa is

;^S ELEMENTS OF MAMMALIAN ANATOMY

a small slit-like opening of the pterygoid (Vidian) canal for
the passage of a branch of the trigeminal nerve. The posterior
palatine foramina are small and are found about one-fourth
the distance forward from the caudal border of the hard palate.
The anterior palatine foramina or foramina incisiva are seen
just back of the incisor teeth.

Viewed from the lateral aspect the skull, after the mandible
has been removed, is elongate with the ventral margin in its
general trend straight, but made emarginate by the presence
of several projections. The dorsal margin is somewhat flat-
tened in the middle but strongly curved at either end. The
surface is convex in both directions and is deeply impressed by
the orbital cavity and temporal fossa. The projections form-
ing the orbital rim and the zygomatic arches are prominent
features of the lateral view. The inner wall of the orbit pre-
sent a number of foramina. These are, beginning with the
most posterior: foramen ovale, foramen rotundum, the orbital
fissure, the optic foramen for the optic nerve, and the spheno-
palatine foramen. A slight depression limited dorsally by a
slightly curved elevated line joins the orbital fissure with the
sphenopalatine foramen. It makes the origin of the external
pterygoid muscle. Immediately in front of and slightly below
the sphenopalatine foramen is the much smaller posterior pala-
tine foramen. The infraorbital foramen pierces the maxillary at
the junction of the malar with the nasal process at the lower
anterior margin of the orbit. Above this is the nasolachrymal
groove and canal. The center of the orbital wall is perforated
by the ethnoidal foramen. A portion of the ethmoid is some-
times visible in the orbit as an irregular area, the os planum,
behind the lachrymal bone.

Viewed from the frontal aspect the outline is nearly circular
when the mandible is present and somewhat greater than a
semicircle with it removed. The most striking feature from
this point of view are the four large openings in the bone frame-
work of the face: the orbits, the nasal aperture, and the oral

THE SKELETON

aperture. The orbits appear almost circular in shape in this
view while the nasal aperture is median and heart-shaped.

Bones of the Disarticulated Skull. — The skull is usually con-
sidered in two parts, the cranium and the face. The former is
composed of nine bones which will be described in order.

The frontal hones (Figs. i6 and 17) are two in number,
lying between the orbits, and articulating with one another

haricl-cd

\ Yonti

p-niy. rna^z llat^y ?>

^1"^

Fig. 16. — Diagram of the Bones of the Mammalian Skull Viewed

Laterally.
I, 2, 3, etc., indicate the places of exit of the twelve cranial nerves, pmx,
Premaxillary; ty, tympanic, 7 and 8 are on periotic; thy, tympanophyal; shy,
stylohyal; ehy, epihyal; chy, ceratohyal; hhy, basihyal; thhy, thyrohyal. The car-
tilage bones are shaded. {From Flower, after Huxley.)

in the median line. They form the roof of the cranial part
of the brain cavity and the caudal portion of the roof of the
nasal chamber. A lateral projection {po, Fig. 17) is known
as the postorbital process. Within the frontal bone is a cavity,
the frontal sinus (Fig. 19), which contains air and is lined with
mucous membrane. It communicates with the nasal cavity.
The lateral descending portion of the bone, articulating with

ELEMENTS OF MAMMALIAN ANATOMY

the palatine and orbitosphenoid, is the orbital plate of the
frontal.

In the majority of the Mammalia the frontal is a paired
bone, but in man the two portions become anchylosed during
the fifth or sixth year. The horns of ruminants are out-

FiG. 17. — Dorsal Aspect of the Cat's Skull.
ap. Anterior palatine foramen; c, canine tooth; co, coronal suture; /, foramina
in palatine bone, the lateral one is the posterior palatine and the medial one is
the sphenopalatine; fr, frontal; if, infraorbital foramen; in, interparietal; Ic,
lachrymal canal at the medial border of the lachrymal bone; Id, lambdoidal
crest; ml, malar; mx, niaxillary; na, nasal; oc, occipital; p, vertical plate of the
palatine; po, postorbital process of the frontal; pm, postorbital process of the
malar; par, parietal; px, premaxillary; sq, squamosal part of the temporal; sg,
sagittal suturo; sp, alisphenoid part of the sphenoid; Ip, temporal fossa; ag,
zygomatic process of the squamosal.

growths of these bones. Among the Cervidse (deer) horns are
usually developed only on the male, and are shed every year.
In the Bovida.^ (cattle) the horns are permanent when present.
The ethmoid (Fig. 19) is a single bone lying ventral to the
frontals and nasals. It separates the cranial cavity from the
nasal cavity and projects into the latter in the form of two
thin scroll-like plates of bone and a median vertical plate.
In order to see the relations of this bone, three skulls must be

THE SKELETON 4I

used, one of which should be bisected sagittally, a second
should have the roof of the cranial and nasal cavities removed,
and the third should be cut transversely on a line joining the
middle of the orbits. The ethmoid is usually visible externally
as a small rhomboid plate on the medial wall of the orbit
between the frontal, lachrymal, and palatine bones. It con-
sists of four parts: the paired clhmoturhinals or lateral ethmoids
(Fig. 19), the mesethmoid, and the cribriform plate. The eth-
moturbinals are in the form of scroll-like lamina} which project
forward from the transverse cribriform plate into the nasal
cavities. The portion which appears externally in the medial
wall of the orbit is the os planum. In the recent state, the
surfaces of these bones within the nasal cavity are covered
with a mucous membrane over which the first pair of cranial
nerves (olfactory) are distributed. The delicacy of the sense
of smell is proportional to the development of the ethmotur-
binals. In most orders of animals live scrolls are present,
but in Echidna there are six and in some Ungulates there are
eight, while in adult Primates there are only from one to three
more, however, being present in the embryo.

The mesethmoid is the perpendicular plate of bone which,
prolonged craniad by cartilage, separates the nasal cavity
into two portions. Caudad it is united to the cribriform
plate, dorsally it articulates with the median descending plates
of the frontals and the nasals, and ventrally it articulates with
the vomer and presphenoid. The cribriform plate is the cau-
dal portion of the ethmoid (Fig. 19), which extending trans-
versely between the frontals, separates the cranial cavity from
the nasal cavity. It is pierced by many pinhole foramina for
the exit of the olfactory nerve. In Ornithorhynchus (duck-bill
of Australia) there is a single large foramen in the cribriform
plate, as is also the case in birds.

The temporal is a paired bone lying at the base and side
of the skull. It contains the organs of hearing. It consists
of four parts: the squamous or expanded portion (Fig. 17),

42 ELEMENTS OF MAMMALIAN ANATOMY

to which the zygomatic process is attached; the mastoid (Fig.
1 8), which is the part caudad of the squamosal and dorsal
to the bulla; the tympanic, which forms the auditory, or tym-
panic bulla; and the petrous (Figs. i8 and 19), which contains
the internal ear. The squamous portion overlaps the parietal
dorsally in a scale-like manner and is limited ventrally by a
clearly defined projecting ridge extending above the external
auditory meatus as the dorsal border of the zygoma.

The zygomatic process extends craniad to join the zygomatic
process of the malar, the two together forming the zygomatic
arch, or zygoma, to which the masseter muscle is attached.
Ventral of the root of the zygomatic process is the mandibular
fossa for the articulation of the condyle of the mandible.
Immediately caudad of this cavity is the postmandibular proc-
ess. The mastoid portion of the bone is somewhat triangular
in shape, about two centimeters long, and lies caudad of the
external meatus.

The tympanic portion appears on the base of the skull as
the tympanic bulla. Its cavity is divided into two unequal
chambers by a bony septum rising from the floor and reaching
almost to the roof. The cranial or true tympanic chamber,
sometimes called the middle ear, is the smaller, and has on
its lateral wall a horseshoe-shaped prominence known as the
tyfnpanic ring, to which the tympanic membrane of the drum
of the ear is attached. There are four apertures in the walls,
of the cranial tympanic chamber: The meatus acusticus externus
or the external acoustic canal; the auditory or Eustachian tube,
leading from the cranial dorsal angle of the chamber to
the pharynx; the fenestra vestibuli and the fenestra cochlece,
opening into the internal ear. The caudal or medial chamber
of the bulla is larger than the cranial, but has no special
features worthy of consideration.

The petrous portion of the temporal bones is not visible on
the external surface of the skull, but. may be seen by looking
into the external acoustic meatus. It forms the medial wall

THE SKELETON 43

of the tympanic cavity. The foramen seen in its dorsal part
is the fenestra vestibuli. In a sagittally dissected skull the
petrous (Fig. i8) may be recognized by the internal acoustic
meatus entering it. By removing the bulla, a large portion
of the petrous bone may be seen from its ventral aspect.
A central prominence, the promontory, contains the fenestra
cochleae opening into the base of the cochlea. The apex of
the promontory, mediad of the fenestra cochleae forms the wall
of the first whorl of the cochlea. Dorsal to the fenestra
cochleae is the fenestra vestibuli, opening into the vestibule of
the internal ear. In the recent state this opening is closed by
a membrane in which is imbedded the foot of the stapes.
The cochlea in the interior of the bone may be displayed by
cutting away the bony rim of the fenestra cochleae and then
chipping off a crust of bone in a line from this foramen to the
juncture of the basioccipital and basisphenoid bones.

The petrous bone, viewed dorsally in a bisected skull,
appears in the floor of the brain cavity ventrad of the tentorium,
the plate of bone partly separating the cerebrum from the
cerebellum. Its surface is pierced by the internal acoustic
meatus, which gives passage to the acoustic nerve. Close
examination reveals a division of the canal into two parts, a
ventral for the eighth nerve and a dorsal, the canalis facialis,
for the facial nerve. This canal twists through the petrous
laterad, and thence between the petrous, squamosal, and mas-
toid to the stylomastoid foramen (Fig. i8, sf).

The parietal bone is paired and joins its fellow in the median
line, forming the caudal half of the sagittal suture. Its point
of greatest convexity is the parietal eminence. Its cerebral
or internal surface presents slight arborescent grooves which
in the recent state sheltered the meningeal artery of the
brain. The plate of bone projecting obliquely craniad from
the caudal border of the parietal is the tentorium, an ossifica-
tion of the dura mater separating the cerebrum from the
cerebellum.

ELEMENTS OF MAMMALIAN ANATOMY
IC

Fig. i8. — Ventral Aspect of the Skull with the Left Auditory Bulla

Removed.

asp, Alisphenoid; ap, anterior palatine foramina; hs, basisphenoid, bl, auditory
bulla; bo, basioccipital; c, canine tooth; e, petrous portion of the temporal; en,
occipital condyle; ea, external acoustic meatus; eh, opening of the Eustachian
tube;/r, frontal; /w, foramen magnum; gc, mandibular fossa; gn, postmandibular
process; hm, hamular process of the pterygoid; ic, incisor tooth; if, infraorbital
foramen; in, incus; jg, jugular foramen; Id, lambdodial ridge; mx, maxilla; ml,
molar tooth; mp, mastoid process; ms, mastoid portion of the temporal; ma,
malar; m, malleus; osp, orbitosphenoid; ov, foramen ovale; p, presphenoid; pi,
palatine; pt, pterygoid; pn, promontory of the petrous; po, postorbital process;
pr, premolar teeth; pm, premaxillary; rd, fenestra cochlear; rl, foramen rotun-
dum; st, stapes; sg, squamosal; sf, stylomastoid foramen; tc, carotid foramen,
or foramen lacerum medius; vm, vomer, forming the septum between the pos-
terior nares; sg, zygomatic process of squamosal.

THE SKELETON 45

The interparietal is a triangular bone situated at the junc-
tion of the two parietals and occipital bones. Its sutures are
usually obliterated quite early.

The occipital (Figs. 17, 18, and 19) is a single bone sur-
rounding the foramen magnum and articulating with the inter-
parietal, parietals, temporals, and sphenoid. In the young
kitten it is composed of four parts: the supraoccipilal, lying dor-
sal to the foramen magnum, the two exoccipitals, lying laterad
of it, and a basioccipital, bounding it ventrally. The cres-
centric elevation on the iupraoccipital near its parietal margin
is the la mbdoidal ridge, to which several muscles are attached.

The exoccipitals bound the cerebellum laterally and sup-
port the occipital condyles, which articulate with the atlas or
first vertebra. Immediately caudad of the bulla is the jugular
process. There are two foramina, one of which, the hypo-
glossal canal, opens ventrally with the jugular foramen adja-
cent to the bulla, while the other, the condyloid canal, opens
more dorsally at the side of condyle. The former trans-
mits the twelfth (hypoglossal) cranial nerve, supplying the
larynx, hyoid bone, and tongue. The jugular foramen, or
foramen lacerum posterius, is at the juncture of the bulla,
exoccipital, and basioccipital. The internal jugular vein and
the ninth, tenth and eleventh nerves pass through it. The
basioccipital portion of this bone lies entirely on the ventral
aspect of the skull. It articulates craniad with the basisphe-
noid by a suture which is generally obliterated in cats three or
four years old.

The sphenoid one lies in the center of the base of the skull.
It is composed of eight parts, corresponding to eight distinct
bones in the lower vertebrates: the basis phenoid, articulating
caudad with the basioccipital; two alis phenoids , extending dor-
sad from the basisphenoid and articulating caudad with the
temporals (Figs. 18 and 19) two pterygoids, projecting ventrally
from the basisphenoid and terminating in sharp processes; a
pres phenoid in the mid-ventral line craniad of the basisphenoid ;

ELEMENTS OF MAMMALIAN ANATOMY

two orhitosphcnoids, extending dorso-laterally from the pre-
sphcnoid and articulating craniad with the frontals. In an
old cat, the sutures between these eight parts become more
or less obliterated. The basisphenoid together with the ali-
sphcnoids is sometimes called the posterior sphenoid in distinc-
tion to the anterior sphenoid, composed of the presphenoid
and orbitosphenoids.

TABLE OF THE FORAMINA OF THE SKULL

Foramina

Bones surrounding
the foramina

Structures traversing the
foramina

InfraorbitaL
Anterior palatine.

Sphenopalatine.

Posterior palatine.

Olfactory f o r a -
mina.

Optic.

Lacerum anterius,
or sphenoidal si-
nus.

Rotundum.

Ovale.

Lacerum medium.

Internal acoustic

meatus.
Canalis facialis.

Stylomastoid.

Jugular or poste-
rior lacerated.
Hypoglossal canal.

Superior maxillary.

Maxillary and p r c •
maxillary.
Palatine.
Palatine.
Ethmoid.

Orbitosphenoid.
Alisphenoid and or-
bitosphenoid.

Alisphenoid.

Alisphenoid.
Petrous and basisphe-
noid.
Petrous.

Petrous, mastoid, and
tympanic.

Tympanic and mas-
toid.
Occipital and tem-
poral.

Exoccipital.

Infraorbital nerve of the superior
maxillary division of the fifth.

Nasopalatine branch of the fifth
cranial nerve and nasal artery.

Sphenopalatine nerve.

Palatine nerve and artery.

Olfactory nerve.

Optic nerve and meningeal artery.
Third, fourth, and sixth cranial

nerves and first division of fifth

cranial nerve.
Second division of fifth cranial

nerve.
Third division of fifth cranial nerve.

Internal carotid artery.

Eighth cranial nerve.

Seventh cranial nerve.

Ninth, tenth, and eleventh cranial
nerves and jugular vein.
Twelfth cranial nerve.

The basisphenoid presents on its dorsal or cerebral surface the
sella turcica, or hypophyseal fossa, which lodges the hypophysis

THE SKELETON

of the brain (Fig. 104). The posterior boundary of this fossa
is the clinoid plate, and its lateral projections are the posterior
clinoid processes. On each side of the basisphenoid there ex-
tends dorsally in a narrow strip to the parietal the alisphenoid,

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at the base of which, craniad of the tympanic bulla, are three
foramina in a line. The most cranial and largest one is the
sphenoidal sinus or anterior lacerated foramen, which transmits
the third, fourth, and sixth cranial nerves supplying the eyeball

48 ELEMENTS OF MAMMALIAN ANATOMY

muscles, and the first branch of the fifth nerve. This foramen
is between the aHsphcnoid and the orbitosphcnoid. The other
two foramina, rolundiim and ovale, transmit the second and
third divisions of the fifth nerve.

The pterygoid portion of the sphenoid is a paired bone
(Figs. i8 and 19) lying on either side of the cranial half of
the basisphenoid and the caudal half of the presphenoid.
In the adult cat the sutures are sometimes obliterated so
that this bone appears as a caudal continuation of the pala-
tine. The two pterygoid bones or plates form the descend-
ing walls, and, together with the median portion of the sphenoid,
the roof of the median pterygoid fossa, whose cranial continua-
tion is the posterior nares. From the ventral posterior angle
of each projects the hamular process, dorsal of which is seen the
small external pterygoid process. Between the bases of the
hamular and the external pterygoid processes is the small
external pterygoid fossa.

The presphenoid hone is the narrow median bone extending
from the basisphenoid to the vomer. It contains within it
two large sinuses into which project the ventral scrolls of the
ethmoturbinal bones. The orbitosphenoids enter into the
formation of the medial walls of the orbits and are perforated
at their bases by the optic foramina, through which pass the
optic nerves.

BONES OF THE FACE

There are seven paired bones in the face and two single
ones, making in all sixteen (Figs. 17 and 18).

The premaxillary, with its fellow, extends ventrad and
laterad of the anterior nares. These bones bear the six incisor
teeth. The anterior palatine or incisor foramina connect the
oral cavity with that of the anterior nares. In life, these
foramina transmit the naso-palatine nerves. In the Primates,
the premaxillary is anchylosed to the maxillary although it
arises from a separate center of ossification.

THE SKELETON 49

The maxillary is a paired bone which meets its fellow in the
median line in the roof of the mouth. All its articulations are
visible externally except those with the maxillo-turbinal, eth-
moid, and vomer. Five teeth, a canine, three premolars, and a
molar, are present in this bone of the adult cat. The molar is
wanting to the young. The several portions of the bone are as
follows: the palatine plate, appearing in the roof of the mouth;
the nasal process, extending dorso-caudad to the frontal; the
process, extending ventrad to the orbit to articulate with the
malar bone; and the orbital plate, which is the roof of the malar
process, forming a partial floor to the orbital cavity. The large
foramen leading from the orbital cavity through the orbital plate
is the infraorbital foramen for the passage of the infraorbital
branch of the superior maxillary branch of the fifth nerve.

The palatine bone with its fellow helps to form the roof of the
oral cavity and the floor of the nasal cavity. It is composed
of two plates: one, vertical, forming the lateral walls of the pos-
terior nares and the cranial part of the walls of the median ptery-
goid fossa, and a portion of the nasal wall of the orbital cavity;
the other, horizontal, forming part of the roof of the mouth.
The vertical plate is pierced by two foramina the posterior
palatine and the sphenopalatine, each of which transmits a
palatine nerve and artery (Fig. 17).

The vomer is a single narrow bone which in the nasal cavity
articulates dorsally with the mesethmoid and ventrally with
the palatines and the palatine plates of the maxfllary, in the
median line. This bone, with the mesethmoid and its cartilage,
forms the nasal septum, dividing the nasal cavity into two
chambers. It is best demonstrated by removing the palatines,
when it may be seen extending craniad from its bifurcated
articulation with the presphenoid to its articulation with the
premaxillaries. The caudal portion of the bone is expanded
horizontally and articulates with the ventral ethmoturbinals.
Its dorsal margin is bifurcated for articulation with the
mesethmoid.

50 ELEMENTS OF MAMMALIAN ANATOMY

The maxilloturbinal is a paired bone occupying the anterior
portion of the nasal cavity (Fig. 19). It is composed of a few
scrolls which, when the nasal bone is removed may be seen
attached to the maxillary. It consists of a horizontal longitu-
dinal plate, whose lateral border is fixed to the maxillary while
the medial border bifurcates into a dorsal curved plate and a
ventral scroll. The space between the maxilloturbinal and
cranial portion of the lateral ethmoid is the middle nasal
meatus. The maxilloturbinal bone in man receives the name
of the inferior turbinated, in distinction to the middle and
superior turbinated bones, constituting the lateral ethmoid.

Fig. 20. — Medial or Inner Aspect of the Mandible.
ang. Angle; cndyl, condyle; cor. pr, coronoid process; can, canine tooth; inc,
incisor teeth; inf. d.fm, inferior dental or mandibular foramen; in, inferior notch;
mol, molar tooth; prtn, premolar teeth; dt, diastema; stn, surface of symphysis; up,
superior notch.

• The nasal bone, joining with its fellow in the median line,
forms a large part of the roof of the nasal chamber. It articu-
lates with the premaxillary, maxillary, and frontal on the
surface, and the ethmoid within the nasal chamber.

The lachrymal bones are two in number and lie on the
cranial part of the nasal walls of the orbits. Each articulates
with the maxillary, frontal, os planum of the ethmoid, and the
malar. The bone has about half of the area of the finger-nail.
The na so -lachrymal canal is bounded by the lachrymal and the

THE SKELETON

maxilla. This canal, beginning in a vertical groove, the naso-
lachrymal groove, carries the duct permitting the tears to pass
from the eye into the nasal chamber (Fig. 16).

The malar bone is paired. It forms the cheek as well as
the lateral and cranial border of the orbit. The arch largely
formed by this bone is the zygoma.
The process projecting dorsad toward
the postorbital process of the frontal
bone is the postorbital process of the
malar. The masseter muscle origi-
nates on the border of the malar.

The mandible or inferior maxillary
is the single bone forming the lower
jaw (Figs. 20 and 22). It is made
up of two halves which are united
by an immovable articulation or
symphysis at the chin. Each half
consists of a horizontal and an as-
cending ramus. On its alveolar
border the horizontal ramus bears

• FlC" 2 1 \^F*NTRAI AsPKCT

three incisor teeth, a canme, two ^^ larynx, Hyoid Bones,
premolars and a molar tooth. In and Tongue.

^ . The tongue has been cut

the caudal part of the medial SUr- transversely near its middle

face of this ramus is the mandibular ryoid^retrL'rroved. ''=
foramen, which transmits the inferior- bh, Basihyai; ch, ceratohyai;

^ . cr, cricoid cartilage of the

alveolar nerve and artery traversmg larynx; eh, epihyai; ep. epi-
the mandibular canal

within the bone to

extending s^°"^^; i^' cricothyroid liga-

^ ment; lyh, thyrohyal; rg, rings
the mental of cartilage of the trachea; tc.

- .^ ^ . ^ r thyroid Cartilage of the larynx I

foramen on the lateral surface near ^^^ tympanohyai; sh. styio-
the base of the canine tooth. The ^y^^-
space on the dorsal border between the canine and the first
premolar tooth is called the diastema.

The ascending ramus or portion of the bone caudad of the
inferior tooth is marked by six features: (i) the fossa on the
outer or lateral surface which gives insertion to the masseter

52 ELEMENTS OF MAMMALIAN ANATOMY

muscle; (2) the angle which is the caiuloventral termination
of the bone; (3) the inferior notch immecHately dorsal of the
angle; (4) the condyle for the articulation with the glenoid
cavity of the temporal; (5) the superior notch dorsal of the
condyle; (6) the coronoid process, which is the dorsal termina-
tion of the ascending ramus and gives insertion to the tem-
poral muscle.

THE HYOID BONES OR HYOID APPARATUS

The hyoid bones consist of two jointed rods, one on either
side (Figs. 21 and 22), hanging from the temporal bone, and
supporting the larynx. Each rod is composed of six parts:
the epihyal; the ceratohyal; the tympanohyal; the basihyal; and
the thyrohyal. The dorsal end of the thyrohyal is prolonged
by a piece of cartilage, the chondrohyal.

The hyoid apparatus varies greatly among mammals. In
man it consists of a single bone composed of the body or
basihyal, two small cornua representing the ceratohyals, and
two large cornua representing the thyrohyals. The bone is
suspended from the skull by ligaments corresponding to the
bony chain in the cat.

LABORATORY STUDIES AND SUGGESTIONS

1. How many more bones are present in the cat than in man?

2. In what two parts of the skeleton does the number of bones in the cat
exceed those in man?

3. What is a sesamoid bone?

4. Find on a specimen a sesamoid bone and describe it.

5. Draw a lateral aspect of the skull and label all parts.

6. What are the paired bones of the cranium?

7. Name the single bones of the face.

8. Draw the caudal aspect of the skull and label all parts.

9. Which bones of the skull derive their names from their location?

10. Which bones of the skull are pierced by more than two foramina?

11. Write a description of the orbital cavity.

12. Which foramina of the skull derive their names from their shape or size?

13. Which foramina derive their names from their location?

14. Which foramina transmit important blood-vessels?

15. Draw figures representing relative shapes and sizes of all foramina of the
skull.

THE SKELETON 53

16. What bones enter into the formation of the brain cavity?

17. Write about 200 words describing the nasal cavity.

18. Draw a ventro-lateral aspect of the tympanic bulla and label all features.

19. Write a description of the tympanic bulla and name some mammals in
which it is absent.

20. Which bones of the skull are composed of more parts in the young than in
the -adult?

21. Name the principal sutures of the skull.

22. Name the parts of the sphenoid bone in the order of size.

23. Name the bones of the skull visible from the dorsal aspect.

24. Name the bones of the skull visible from the cranial aspect.

25. W'hat bone of the cranium paired in the cat is single in man?

26. What bone present in face of the cat is wanting as a separate element in
man?

27. Draw lateral aspect of mandible and label all features.

28. Name the bones bearing the teeth.

29. Name the elements of hyoid apparatus in order.

30. Draw a section of the frontal bone showing diploe.

31. Describe the difference between the relative locations of the cranial and
facial portions of the skull in cat and man.

S2. Name five membrane bones and five cartilage bones.

VERTEBRAE

The vertebral column is composed of the following five
groups of vertebrae; seven cervical, thirteen thoracic, seven
lumbar, three sacral, and caudal varying from four to twenty-
six. The following six features are common to all of the verte-
brae in the first four groups except the atlas: (i) the body
of the vertebra (Fig. 23), which forms the floor of the neural
canal and articulates with the adjacent vertebra by means of
interposed discs of cartilage; (2) the transverse processes, which
project laterad from the body or from the walls of the neural
canal; (3) a spinous process, which projects dorsad from the
roof of the neural canal; (4) the vertebral arch, composed of a
pedicle on either side, forming the ventrolateral walls of the
vertebral canal, and the la mince, extending dorsad from the
pedicles to complete the dorsal wall of the neural canal; (5)
the intervertebral notch, which, with the notch of the succeeding
vertebra, forms the intervertebral foramen for the exit of a
spinal nerve; (6) the articular processes, two of which project

ELEMENTS OF MAMMALIAN ANATOMY

craniad and two caudad from each vertebra. I'he former are
called the anterior articular processes and the latter posterior
articular processes.

The first certical vertebra, or atlas, is characterized by its \

large horizontally expanded transverse ear-shaped processes.

THE SKELETON 55

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ELEMENTS OF MAMMALIAN ANATOMY

Fig. 23.-

the absence of a spinous process, and its rudimentary body.

Its true body in the embryo becomes united to the axis as the

odontoid process. The cranial margin
of the vertebral arch is prolonged at
each side into a process or articulation
with the occipital condyles (Fig. 18)
of the skull. The root of this articular
n^:-] process is pierced by a foramen giving
\?^ passage to the first spinal nerve and
the vertebral artery and vein (Fig. 24,
fr). From the lateral opening of this

-Plan of a Ver- . . ^ . . i.* 1

TEBRA. foramen {fr) a groove is continued

s/). Spinous process; ar, ygntrad to the middle of the transverse

articular process; MS, trans- . , , . ,

verse process; nc, vertebral prOCCSS, whcrC it Icads intO the traUS-

LT' "'tntrut'orboX: '^erse foramen common to the first cer-

vical vertebrae. The vertebral artery
and vein course through this canal (Fig. 24).

The epistropheus (axis), or second vertebra, is characterized
by its dens or odontoid process, which
projects within the atlas, and also by
its elongated spinous process which
projects both craniad and caudad.
The transverse process projects
caudad from the body, which is flat-
tened dorsoventrally. This process
is pierced at its base by the transverse
foramen.

The remaining five cervicals are
very similar to one another. The
seventh has no transverse foramen.
The spinous processes grow suc-
cessively longer from the third to
The transverse processes of the fourth and fifth are bifurcated,
the dorsal branch being called the transverse element and the
ventral one the costal element, since it is really the rudiment

Fig. 24. — DoRsocAUDAL As-
pect OF Atlas.
Ir, Transverse process; nc,
neural canal; sp, spinous
process; fr, aperture of the
transverse foramen which
enters the atlas at vf; azg,
anterior articular process; zg,
posterior articular process.

the seventh (Fig. 22).

THE SKELETON

of a rib. The transverse process of the fifth ends in three
branches. The following features are common to all thirteen

-oiht

y^^^ acd.

Fig. 25. — Lateral Aspect of the Epistropheus.
ar. si. Anterior articular process; od. pr, odontoid process; nl. sp, neural spine
or spinous process; p. zg, posterior articular process; trs. pr, transverse process;
vrt. c, transverse foramen.

thoracic vertebrae: a spinous process, projecting from the dor-
sum of the neural arch; two cranial
articular processes, facing dorsad or
dorsolaterad; two caudal articular
processes, facing ventrad or ventro-
mediad; a body whose transverse
diameter is greater than the vertical
diameter; and transverse processes.
There are two half facets on each
side of the body of every thoracic

vertebra except the first, eleventh, ^f^lf'^^Mi^l^V^i!
twelfth, and thirteenth. The head ^^ "■'

r '^ J^^ i.' 1 4- ' t-'U 4^„r^ FiG. 26. — LaTEROCAUDAL

of a rib thus articulates with two ^^^^^^ ^^ ^^^ s^^^^^^

vertebra (Fig. 29). The body of Thoracic Vertebra.

the first vertebra bears on each tr. Transverse process;

, ,^ - ce, neural canal; ar, face

side a whole facet and a nan lacet. for tubercle of rib; ar, pos-

The eleventh, twelfth, and thir- ^erior articular process; 5.
J. XIV. viv. V v.ixi,ix, u , spinous process; c, centrum;

teenth bear a whole facet on each n, intervertebral notch; e,
. . . ,, , , pedicle; /, lamina.

side of the body.

The transverse processes of the first eleven bear facets for
the articulation with the tubercles (Fig. 26) of the ribs. The

58 ELEMENTS OF MAMMALIAN ANATOMY

last three thoracic vertebrae are characterized by mammillary
processes springing from the dorsolateral portion of the roots
of the anterior processes.

The following features are common to all of the lumbar
vertchrce: a spinous process projecting dorsocraniad (Fig. 27);
a transverse process projecting ventrocraniad on either side
from the body; anterior articular processes and posterior articu-
lar processes. A mammillary process is present on the root
of the anterior articular process of the first five bones, and an
accessory process occurs on the caudal margin of the wall of
the neural arch of all except the last vertebra. The transverse
processes increase in length and curvature caudally. The spin-
ous processes increase in length in the same order, and the
neural canal likewise enlarges caudally.

The sacrum is a single bone (Fig. 28) formed by the union
of three sacral vertebras. The limit of each element is marked
by the dorsal and ventral intervertebral foramina which fur-
nish passage for the dorsal and ventral branches of the spinal
nerves. The two tubercles on either side of each of the three
median spinous processes are the result of the fusion of the
articular processes. The cranial portion of the bone presents
on its lateral aspect the auricular surfaces for articulation with
the ilium. This expansion appears to be a modified transverse
process. Prominent transverse processes also project from the
caudal angles.

The caudal vertebrae vary greatly in number. According
to Mivart, there are only four in the Manx cat; and according
to Jayne, there may be as many as twenty-six in some varieties
of the common cat. The transverse processes and articular
processes become less prominent from the third vertebra to
the eighth or ninth, where they are present only as slight ridges.
The spinous process is present in the first three, but dwindles
to a ridge in the fourth. The first six or seven elements possess
a neural arch which more distally loses its roof, making the
neural canal a mere groove. The groove becomes fainter dis-

THE SKELETON

tally and finally disappears entirely. The chevron bones are
the paired ossicles projecting ventrad from the cranial ends
of the bodies of the vertebra}, from the second or third to the
thirteenth vertebra. In the sixth, seventh, and eighth verte-
brae the chevron bones unite ventrally in the middle Hne,
forming an arch. The last ten caudal vertebrae are scarcely
more than cylinders of bone representing the bodies of the
vertebrae.

Fig. 27. — Caudal Aspect of Fourth
Lumbar Vertebra.

a. Accessory process; cr,' centrum
or body; pa, pedicle; tr, transverse
process; s, neural canal; sp, spinous
process; zg, the mammillary process
of the anterior articular process; am,
lamina; pz, articular process.

Fig. 28. — Dorsal Aspect of the
Sacrum.

fl. Floor of the neural canal; fr,
dorsal aperture of the intervertebral
foramen; //, lateral mass; pzg, poste-
rior articular process; sp, spinous
process; si, aurictilar surface for artic-
ulation with the ilium; zgt, tubercle
formed by fusion of the articular proc-
esses; zg, anterior articular processes.

The number of vertebrae in the different species of mammals
varies widely. As a rule, there are seven elements in the
cervical region. The sea cow (Manatus) has only six cervical
vertebrae, while the three-toed sloth has nine. The number
of thoracico-lumbar varies from sixteen in the organ to thirty-
six in the cetacean Delphinus. The elements composing the
sacrum likewise vary from one in the ape, Cercopithecus, to

ELEMENTS OF MAMMALIAN ANATOMY

nine in some of the Edentata. The human sacrum is composed
of from four to six vertebra'. The same is true of the gorilla,

Fig. 29. — Ventr.^l Aspect of the Bones of the Thorax. The numbers
on the vertebral or bony portions of the ribs indicate the names of the ribs. The
numbers of the last four ribs are placed just craniad of them,

c. Cartilaginous part of the first rib; cr, cartilaginous disc between the bodies
of the vertebrae; en, xiphoid process; hd, heads or capitula of ribs; m, manubrium;
mr, attachment of twelfth to the eleventh rib; n, free termination of thirteenth
rib; r, attachment of the eleventh to the tenth rib; /6, tubercle of first rib; /n,
transverse process of first thoracic vertebra; v, body of vertebra.

chimpanzee, and orang. The caudal vertebra? vary greatly
in number in the different forms. In the adult human there
are present only four or five vertebra?, which form a single

THE SKELETON 6 I

bone, the coccyx, while in the embryo eight segments make up
the caudal region. Ossification takes place, however, in only
five or six segments.

THE STERNUM

The sternum of the cat is composed of eight pieces, called
steniebrcB, which lie in the median line on the ventral side of
the chest (Fig. 22). The sternum serves for the attachment
of the cartilaginous portions of nine pairs of ribs. The first
sternebra (Fig. 29), which ends craniad in a laterally com-
pressed pointed process is the manubrium. The six succeed-
ing sternebrae form the body or corpus sterni ; the caudal piece
is called the xiphoid process. It is terminated by a flat piece
of cartilage. The cartilaginous portion of the first rib articu-
lates with manubrium near its middle. The ribs from the
second to the seventh inclusive are attached at the junctions
of the sternebrae. The eighth and ninth ribs are attached near
together on the caudal end of the seventh sternebra.

RIBS

There are thirteen pairs of ribs in the cat. The nine cranial
are called true ribs because they articulate dorsally with the
spinal column and ventrally with the sternum. The other
four (Fig. 29) are false ribs, three of which articulate ventrally
with other ribs, while the fourth has no ventral articulation, and
is therefore called a floating rib. Each rib is composed of two
parts, the vertebral or bony portion and the sternal or cartilagi-
nous portion.

The following description of the sixth will serve to give a
correct idea in general of the anatomy of a rib. Its vertebral
portion (Fig. 30) presents four features: a head or capitidum,
which articulates with the bodies of the fifth and sixth thoracic
vertebrae; a tubercle, which articulates with the transverse proc-
ess of the sixth thoracic vertebra; a neck, which is the con-

ELEMENTS OF MAMMALIAN ANATOMY

stricted portion between the capitulum and tubercle; and the
shaft, including the portion of the rib l^etwcen the tubercle
and its articulation with the sternal or cartilaginous portion.
The bend in the shaft beyond the tubercle is the angle. The
sternal portion of the rib, consisting of cartilage, is sometimes

called the costal rib. In the sixth rib
the costal portion is about half as long
as the vertebral portion.

Certain ribs present marked features
varying from the sixth. The first rib is
stout and flat and has no distinct angle.
The articular surface of its head is not
divided into two facets, as is the case in
all the others except the three caudal
ones. The lengths of the ribs increase
from the first to the ninth. The last
three ribs have no necks and no tubercles
for articulation with the transverse proc-
esses of the vertebrae.

The number of ribs varies from nine
ag, Angle; cr, pit for pairs in the cctaccan Hyperoodon to

articulation with car- ^ . .^jij-u

tiiaginous portion; h, twcnty-four m the two-toed sloth

(Cholcepus). In most fishes and snakes,
ribs are present throughout both the
trunk and tail regions, but with the
assumption of life on land, and the de-
velopment of Hmbs, the vertebrates have suffered a de-
generation of the ribs in all parts except the middle portion
of the trunk. In the embryo, however, anlage (beginning)
of ribs occurs in all regions of the trunk, but they early
coalesce with the vertebrae except in the thorax.

LABORATORY STUDIES AND SUGGESTIONS
I. Draw caudal aspect of third thoracic vertebra and label all features.
Describe the differences between the first and last thoracic vertebrae.

Fig. 30. — Caudal As-
pect OF Sixth Rib.

capitulum; nk, neck;
sh, shaft; th, tubercle
with facet for articula-
tion with transverse
process.

3. What feature common to all thoracic vertebrae not present on any of the
other vertebrae?

THE SKELETON 63

4. Draw the caudal aspect of the fourth cervical vertebra.

5. What feature common to all cervical vertebrae except seventh but not
present in any other vertebra?

6. Draw cranial aspect of atlas and label all features.

7. Compare the third and seventh cervical vertebrae.

8. What two features serve to distinguish the lumbar from all other vertebrae?

9. Draw the cranial aspect of the second lumbar vertebra and label all
features.

10. Wherein does the seventh lumbar vertebra differ from the first?

1 1 . How do you distinguish the caudal from the cranial aspect of any vertebra?

12. Draw ventral aspect of sacrum and label all features.

13. Give the two features distinguishing the caudal vertebrae from all others.

14. Note the size and direction of the spinous process throughout the column.

15. Describe the variation in number of the different groups of vertebrae in
other mammals.

16. Draw lateral aspect of sternum and label all features.

17. Describe the attachment of ribs to sternum.

18. What features common to all the ribs?

19. Name ribs having a tubercle.

20. Draw first rib and label all features.

21. Draw cranial aspect of ninth rib and label all features.

22. How do you distinguish a false rib from a true rib?

23. What features make the caudal aspect of a rib?

24. Make a drawing showing the articulation of a rib with the spinal column
and label all parts.

25. How do ribs vary as to number in mammals?

THE THORACIC LIMB

The thoracic or fore-limb of the cat is composed of a scapula,
clavicle, humerus, ulna, radius, seven carpals, five metacarpals,
and fourteen phalanges (Fig. 22). The scapula and clavicle
form the shoulder girdle.

The scapula, commonly called the shoulder-blade (Fig. 31),
is not articulated with the bones of the trunk, but is held in posi-
tion by the serratus magnus, levator anguli scapulae, and other
less important muscles. It articulates with the head of the
humerus by the glenoid cavity. It presents three well-marked
borders: the cranial or anterior, the vertebral, and the axillary
adjacent to the vertebrae on the side near the axilla or armpit.

ELEMENTS OF MAMMALIAN ANATOMY

The outer surface of this bone is divided by a strong spine into
two nearly equal fossa?, the cranial of which is the supraspinous,
and the caudal one the infraspinous, fossa. From the lower
part of the spine project the acromion and mclacromion proc-

/-A

^-r/^

Fig. 31. — Lateral or Outer Aspect of the Scapula.
ac. Acromion process; ax, axillary border; c, coracoid process; gl, glenoid cavity;
m, metacromion process; sc, scapular notch; sp, spine; sup. fos, supraspinous
fossa; vr, vertebral border; n, neck.

esses. The subscapular fossa occupies the entire inner or

medial surface.

A slight constriction between the base of the spine and the

margin of the glenoid cavity
is termed the neck. From the
cranial side of the latter the
coracoid process curves mediad.
The clavicle is a slender
curved bone, about one inch
long, imbedded in the muscle

between the manubrium and the coracoid process (Fig. 22).

It does not articulate with any bone, but is held in place

by the cephalohumeral and cleidomastoid muscles (Fig. 49).
The shoulder girdle varies somewhat among the Mammalia.

The clavicle is never fully developed in any of the Carnivora.

Primates, Chiroptera, Edentata, and Monotremata are the

Fig. 32. — Caudal Aspect of Left

Clavicle.

b. Medial end; a, lateral end.

THE SKELETON

only orders in which all the species possess clavicles. A third
element of the shoulder girdle, known as the coracoid, is a fully
developed bone only in the Mono-
tremata, where it articulates at one
end with the scapula, forming part of
the glenoid cavity, and at the other
end with the presternum. In the
other mammals the coracoid is rep-
resented by the coracoid process of
the scapula, which ossifies from a
separate center. In many of the
lower vertebrates a distinct coracoid is
present.

The humerus is the bone of the arm
or brachium. It articulates proximally
with the glenoid cavity of the scapula
(Fig. 22) and distally with the ulna and
radius. It consists of three parts, the
proximal extremity bearing the head,
the middle portion or shaft, and the

. /-r^. X rr^i Fig. 33.— Cranial Aspect

distal extremity (Fig. 33). The greater of Right Humerus.
and lesser tuberosities separated by the ^^' ^'Tl^^^l ^':°°^^"' 'I'

^ -^ supracondyloid ridge; cp,

bicipital groove lodging the tendon ofcapitulum for articulation
. 1 , . , .1 . with the radius: dr, deltoid

the biceps muscle, are the two processes ^-idge; et, external condyle;

on the proximal extremity. The for-s^- greater tuberosity; it.

internal condyle; It, lesser

mer is the larger and more craniad tuberosity; sp, supracondy-
and serves tor the insertion of the'^,J:^'Z:mZ .r'sut

SUpraSpinatUS muscle (Fig. 55). The inator ridge; /r, trochlea for
... . . Ill • articulation with ulna.

distal extremity is marked by two im-
portant projections, the external and internal condyles. Ex-
tending proximad from the external condyle is the supinator
ridge. Proximad of the internal condyle is the supracondyloid
foramen transmitting the median nerve and branchial artery
(Figs. 78 and 100). The olecranon fossa is the deep cavity on the
caudal aspect of the bone, opposite the coronoid fossa. The

ELEMENTS OF MAMMALIAN ANATOMY

articular surface of the distal extremity consists of the capitidiim
for articulation with the head of the radius, and the trochlea
for articulation with the semilunar notch of the ulna. On
the cranial side of the proximal third of the
bone is the rough deltoid ridge for the inser-
tion of the deltoid muscle which arises
from the shoulder girdle.

The ulna is the longest bone of the fore-
arm or antchrachium, and is caudad of the
radius. It articulates in the semilunar
notch with the trochlea of the humerus and
in the radial notch with the head of the
radius. The distal articulation is with the
radius, triquetral and pisiform (Fig. 22).
The olecranon process forms the proximal
termination of the bone and serves for the
insertion of the triceps muscle. Distad of
the semilunar notch is a projection known
as the coronoid process. The styloid process
forms a small projection on the distal
extremity of the bone.

The radius is the preaxial or cranial bone
of the antebrachium. It articulates prox-
„ *^^ ^ imally with the capitulum of the humerus

Fig. 34. — Lateral -^ . i r i i i j* n

OR Outer Aspect of and the radial notch of the ulna, and distally
"Z.^lr"Iu^Z'-tcet with the scapholunar and ulna. It bears
for radius; cr. coro- but two proccsscs, the tiihercU and the styloid

noid process; gs, , rr^i . 7 7 /-r-- \ • r 1,4-

semihinar notch; Is, proccss. The tiihercle (Fig. 35) IS a slight
radial notch; on, oie- ^^^^ ^^^^ ^^^ proximal end in the ulnar

cranon process; st, ^

styloid process. side. Proximal from the tubercle is the

neck which supports the head bearing a
concave crown for articulation with the capitulum of the
humerus. The styloid process projects from the distal end
parallel with the process of the same name on the ulna.

THE SKELETON

The bones of the antebrachium in many mammals are more
or less coalesced. In the Chiroptera and many of the Ungu-
lates the radius is enlarged at the expense of the ulna, whose
proximal third only remains. The primitive Ungulates of the
lower tertiary period possessed a complete
ulna as well as radius. The phylogeny of k

the horse's limb illustrates the gradual de-
velopment of the antebrachium of the
Equidae (Fig. 36). Fossil remains reveal
the fact that mammals existed as early as
the triassic period, when the sedimentary
rock forming the triassic strata was laid
down. This probably occurred 80,000,000
years ago.

According to paleontological investiga-
tions, the Ungulata probably arose from
the Condylarthra, a group of small five-
toed mammals of the lower Eocene, best
represented by the typical genus Phenacodus.
In this genus and its successor, Hyracother-
ium, the ulna and radius are well developed
and distinct. Orohippus, the descendant

Fig

. 35. — Medial

of Hyracotherium, also shows a distinct °^ ^^^^^ Aspect of

Right Radius.

radius and ulna, but in the later forms of
the horse line the ulna gradually dimin-

fc, Articulatory sur-
face for capitulum
of humerus; hd, head

ishes in size and becomes more and more —the point of the

arrow is on the ar-
ticulating surface for
the radial notch; nk,
neck; sc, articulatory
surface for scapho-
lunar; st, styloid proc-
ess; tb, tubercle; ul.

coalesced with the radius, until in Equus
scarcely more than the proximal third
remains (Fig. 38).

Carpus.— The carpus consists of seven
bones arranged in two rows (Fig. 37). Be- facet for ulna.
ginning on the pollex (thumb) side, the
scapholunar, triquetral, and pisiform compose the proximal
row, and the greater multangular, lesser multangular, capitate,
and hamate form the distal row. The scaphohinar, easily dis-

ELEMENTS OF MAMMALIAN ANATOMY

tinguished because of its large size, articulates with the radius,
triquetral, hamate, capitate, lesser and greater multangular.
The triquetral articulates with the ulna, hamate form, pisiform,
and scapholunar. The pisiform is next to the scapholunar in

Fig. 36. — {See next page for explanation.)

size. It projects prominently laterad from the triquetral and
articulates with the ulna and triquetral. The greater multangu-
lar is crescentic in shape and articulates with the scapholunar,
lesser multangular and first and second metacarpals. The

THE SKELETON

lesser multangular is distinguished by its flatness. It articulates
with the scapholunar, capitate second metacarpal, and greater
multangular. This bone is not visible on the palmar surface

Fig. 36. — Genealogy of the Horse.
F, Forefoot; H, hindfoot; A, forearm; L, leg; 7, Orohippus; II, Mesohippus;
III, Miohippus; IV, Protohippus; V, Pliohippus; VI, Equus; 2, 3, 4 and 5 are
the second, third, fourth, and fifth digits respectively; mc, metacarpus; mt,
metatarsus; p, phalanges; ?<, ulna; r, radius; /, tibia;/, fibula. — {After Marsh.)

of the wrist. In the cat the lesser multangular is larger than
the greater multangular. The capitate articulates with the

ELEMENTS OF MAMMALIAN ANATOMY

scapholunar; lesser multangular, hamate and second, third, and
fourth metacarpals. The hamate can be recognized by its
wedge shape. It articulates with the scapholunar, triquetral,
capitate and fourth and fifth metacarpals. Each carpal bone

develops from a single center
except the scapholunar, which
develops from two centers.

The typical arrangement of
the vertebrate carpus is shown
in figure 37, B. The pisiform
does not belong to the cartil-
aginous skeleton, but is a sesa-
moid bone. In all mammals

A. B.

Fig. 37.

A, Dorsal aspect of left manus of cat; a, first phalanx of the pollex; h, second
or terminal phalanx; en, triquetral; h, head of fourth metacarpal; m, capitate;
mt, metacarpal 4; n, claw; pi, pisiform; s, sesamoid bone; st, scapholunar; Id,
lesser multangular; Im, greater multangular; u, hamate; 1,2, and 3, first, second,
and third phalanges of the middle digit.

B, Generalized type of carpus as found in lower vertebrates: c, Centrale; i,
intermedium or lunare; r, radiale or scaphoid; ra, radius; m, metacarpals; u,
ulnare or cuneiform; ul, ulna; i, carpalia i, or trapezium; 2, carpalia 2, or trape-
zoid; 3, carpalia 3, or magnum; 4, and 5, carpalia 4 and 5, or unciform.

possessing five digits, the anlage of three bones in the proximal
row, five bones in the distal row, and a central element occurs
in the embryo, but through fusion of elements a less number is
present in most adults. Thus, in the cat the radiale and inter-
medium and centrale unite to form the scapholunar. In all
forms carpalia 4 and 5 coalesce to form the hamate.

Metacarpus. — There are five metacarpal bones forming the
middle region of the forefoot. They are named, beginning on

THE SKELETON

the pollex side, first, second, third, fourth, and fifth metacarpals
respectively. Each bone consists of a proximal extremity or
base, a middle portion of shaft, and
a distal extremity or head (Fig. 37).
These bones are curved so as to be
slightly convex on the dorsal aspect.
The number of metacarpals in
mammals varies from one in Equus
to five which arc present in most
orders. Nearly all the species of
every order, except the Edentata
and Ungulata, possess five metacar-
pals. In the pig and hippopotamus
there are four metacarpals, in the
rhinoceros three, and in the camel,
deer, sheep, and cow two. In the
last three forms the metacarpals
present are the third and fourth,
which in the adult are coalesced
into a single bone known as the
cannon-hone. Remnants of the
second and fifth metacarpals are
present in the deer, sheep, and cow,
as the small caudo-lateral hoofs indi-
cate. The functional metacarpal Fig. 38.— Lateral Aspect of

. , . , 1 • 1 Left Forelimb of Equus.

present m the horse is the third, h, Humerus; mz, third meta-

The reduction of metacarpals in the ^^"p^^^ f ^' ^^^^^^ metacarpal;

^ p, phalanges; r, radius; s,

ancestral forms of the horse is sesamoid; sc, scapula; ua, ulna;

^ ' r /- ^ •^^ ^ <!. navicular; c, lunate; m, tri-

shown m figure 36, and will be re- q^^tral; n. pisiform; w, capi-

ferred to again in the description of ^^^^J "• hamate.
the phalanges.

Phalanges. — The cat has five toes or digits on the forefoot,
called pollex, index, medins, annulus, and minimus. Each
digit, except the pollex, consists of three phalanges (Fig. 37).

72 ELEMENTS OF MAMMALIAN ANATOMY

The poUcx or thumb has only two phalanges. The row of
phalanges articulating with the metacarpals is called the proxi-
mal, the terminal row the distal, and the remaining row the
middle phalanges. Two small sesamoid bones are attached on
the volar side of the junction of each proximal phalanx with
the metacarpal. Each distal phalanx has its proximal end
produced caudal on the palmar aspect so that its articular
surface faces dorsal. The distal phalanges terminate in claws
whih are retractile.

The number of digits in the forefoot of Mammalia varies
from one to five. Nearly all the species of every order except
the Edentata and Ungulata possess five digits (pentadactyl).
The tapir has four functional digits (tetradactyl). The cow,
deer, sheep, and pig also have four digits, but only two are
functional (didactyl), the second and the fifth being atrophied
and terminating in the small caudo-lateral hoofs which do
not touch the ground. The rhinoceros has three functional
digits (tridactyl), and the Equida^ possess only one digit (mono-
dactyl) (Fig. 38), the third, though the atrophied remnants
of the second and fourth metacarpals are present as splint bones
which do not support phalanges.

As before stated, the Ungulates are undoubtedly descendants
of a five-toed ancestor of Eocene times. The evolution of the
horse's limb and the reduction in the number of digits are shown
in figure 36. Fossil remains of the ancestors of the horse have
been found in western United States, Europe, and South
America. Orohippus lived in the region of Wyoming, Mon-
tana, and Idaho probably more than 5,000,000 years ago,
when that country was more or less marshy, and it was neces-
sary that the mammals should possess a spreading foot which
would not permit them to sink too deep into the mud. As the
ground become firmer and preying Carnivora more numerous,
the foot of the horse became adapted to rapid flight over solid
ground. Thus, through the process of evolution the third
digit w^as enlarged at the expense of the other digits. Confir-

THE SKELETON 73

mation of this ancestral history of the horse is found by an
examination of the early embryonic stages. According to
Ewart, a horse embryo 35 cm. long possess quite well-devel-
oped second and fourth metacarpals terminating with phalan-
geal structures. The ulna and radius of an embryo 50 mm. long
are strikingly similar to these same bones in Mesohippus.
In a still younger embryo the ulna is complete and corre-
spondingly as large as in Orohippus.

As to the method of walking, mammals are spoken of as
plantigrade, digitigrade, ungtdigrade, and rectigrade. The first
mode of progression is exemplified by the bear, which places
its metacarpals and phalanges flat on the ground in walking.
The cat is digitigrade, walking on its toes. The horse and cow
are unguligrade, as they walk upon the hoof. The elephant
is rectigrade, the entire weight resting on a large pad, and the
foot immobile. In some cases, as in the Cetacea, the forefoot
is adapted for swimming instead of walking, and the number of
phalanges to each digit is more than three.

LABORATORY STUDIES AND SUGGESTIONS

1. What bones compose the shoulder girdle?

2. How is the thoracic limb attached to the trunk?

3. What does the condition of the clavicle in the cat indicate as to its past
history?

4. Draw the medial aspect of the scapula and label all parts.

5. What is the significance of the coracoid process?

6. Which processes of the scapula derive their names from their location and
which from their shape?

7. How do you distinguish the right from the left scapula?

8. Draw the caudal aspect of the humerus and label all features.

9. Describe what is seen in looking directly at the distal articulating surfaces
of the humerus.

10. How do you distinguish the right from the left humerus?

11. What features of the humerus derive their names from their shape?

12. Draw the medial or inner aspect of the ulna and label all features.

13. What features of the ulna derive their names from their form?

14. How do you distinguish the right from the left ulna?

15. Describe the articulations of the radius.

16. Draw lateral aspect of radius and label all features.

74 ELEMENTS OF MAMMALIAN ANATOMY

1 7. Describe the condition of the bones of forearm in the horse and its ancestors.

18. In a five-month fetus of the horse the ulna is distinct from radius and
complete, while in the mature animal but little more than the distal third re-
mains, and is anchylosed to the radius. Explain significance of this fact.

19. Draw ventral aspect of carpus and label all parts.

20. Wherein is the chief difference between carpus of cat and man?

21. Draw the lateral aspect of the third metacarpal and label all features.

22. How do you distinguish the distal from the proximal end of the metacar-
pals?

23. Describe the variation in the number of metacarpals in mammals.

24. Describe the usual arrangement of the phalanges in mammals having five
digits.

25. How do you distinguish a phalanx from a metacarpal?

26. Give the number of functional digits in forelimb of dog, pig, cow, sheep,
horse, and rabbit.

27. Name some mammals with atrophied digits.

28. What is the significance of these?

29. In the evolution of the perissodactyls (odd-toed ungulates) describe the
order in which the digits are lost.

30. In the Bovidae and Cervidas which two digits are functional?

THE PELVIC LIMB

The pelvic or hind-limb of the cat is composed of the innomi-
nate bone, femur, patella, tibia, fibula, seven tarsals, five
metatarsals, and twelve phalanges.

The coxal or hip bone is composed of four parts, the ilium,
ischium, pubis (Figs. 22 and 39), and the small acetabular or
cotyloid bone. The ilium is the dorsal portion, extending down
to and occupying about one-third of the acetabulum. The
ischium includes the caudal portion of the bone, extending ven-
tral and forming two-thirds of the boundary of the obturator
foramen. The pubis is the ventral portion, possessing two rami,
one projecting laterad to unite with the ilium, cotyloid, and
ischium, and the other projecting caudad along the mid-ventral
line, joining its fellow and the ischium. In young kittens the
junction of these parts is plainly visible, but in adult specimens
it is wholly obliterated. In old specimens the ischium and
pubis become more or less anchylosed with their fellows in the
mid-ventral line. The cranial and dorsal border of the ilium
is the crest (Fig. 40). The rough crescentic area on the medial

THE SKELETON

aspect is the auricular surface for articulation with the sacrum.
The cranial rounded angle of the crest is the anterior superior
spine. The anterior inferior spine is the small prominence
craniad from the ventral termination of the auricular surface.

The ischium presents a spine on its dorsal border near the
acetabulum. Between this spine and the posterior inferior

Fig. 39. VeNTRO-L ATER AL

Aspect of Left Coxal Bone of
A Kitten.

ct, Cotyloid bone; ac, acetabu-
lum; il, ilio-pectineal eminence;
as, anterior inferior spine. (Mod-
ified after Jayne.)

Fig. 40. — Ventral Aspect of the
Coxal Bones.
ac. Acetabulum; ai, posterior inferior
spine; ar, auricular surface; cr, crest;
et, cotyloid notch; ip, iliopectineal emi-
nence; is, body of ischium; ob, obturator
foramen; pb, body of pubis; s, spine;
sm, symphysis pubis; sp, spine of pubis;
sr, surface of ilium for attachment of
spinal muscles; tb, tuberosity of the
ischium.

spine of the ilium, is a shallow concavity termed the greater
sciatic notch in distinction to the lesser sciatic notch between
the spine of the ischium and the tuberosity. The acetabulum
or cotyloid cavity forms the cup for the articulation of the femur.
The interruption in its ventral border is the cotyloid notch,
at whose base there is a depression for the attachment of the

y6 ELEMENTS OF MAMMALIAN ANATOMY

ligameniinn teres holding the femur in place. The junction of
the pubis with its fellow is known as the symphysis. The
cranial portion of the bone lying on either side of this is called
the body, the caudal part taking the name of ramus. The latter
forms part of the boundary of the obturator foramen and meets
the ramus of the ischium. This foramen gives passage to the
obturator nerve and vessels.

In the Sirenia, which have no pelvic limbs, the innominate
bones are rudimentary. In the Cetacea these bones are also
rudimentary, which fact indicates that the ancestors of these
forms possessed functional hind-limbs.

The femur, or thigh-bone, may be recognized by its spherical
head with a pit for the attachment of the ligamentum teres
which aids in holding the head in the acetabulum.

The greater trochanter projects from the proximal end of the
bone to a level with the head. On this process are inserted the
pyriformis, gluteus medius, and gluteus minimus muscles, all
of which originate on the innominate bone. The lesser tro-
chanter is the small projection on the caudal aspect of the proxi-
mal portion of the bone (Fig. 41). The intertrochanteric ridge
or posterior intertrochanteric Une extends between the two
trochanters, and lying between this line and the neck is the
digital fossa. The external and internal condyles are the articu-
latory processes on the distal end of the bone. The blunt
projections at their roots are the external and internal tuberosi-
ties. The intercondyloid notch forms the depression on the
caudal aspect between the condyles. On the cranial aspect is
the trochlear surface for articulation with the patella. Two
small sesamoid bones, the fabellae, are present on the caudal
aspect of the condyles, but they are usually removed in prepar-
ing the skeleton. The linea aspera is the slightly roughened line
beginning on the caudal side, distal to the middle and extending
proximally a short distance, where it bifurcates.

The form of the femur varies but little among mammals
having functional posterior limbs. No living Sirenia have any

THE SKELETON

trace of a femur, but a vestigial femur is present in Halilhermm,
a fossil form. The hind-limbs are wanting among the Cetacea,
but in a few forms nodules of bone or cartilage may represent

i.cnd.l

Fig. 41. — Caudal Aspect of Femur.

ex. tub. External tuberosity; int. tub,
internal tuberosity; ex, end, external con-
dyle; int. end, internal condyle; i, end, t,
intercondylar notch or fossa; inleh. r, in-
tertrochanteric ridge; g. Ireh, greater tro-
chanter; hd, head; lin, as, linea aspera; pit,
pit for the ligamentum teres; tr. fos, tro-
chanteric fossa or digital fossa.

Fig. 42. — Anterior or Cra-
nial Aspect of Right Tibia.
at, Articulatory surface for
the ankle bone; er, crest; et,
external tuberosity; /c, facet for
articulation with the fibula;
im, internal malleolus; it, in-
ternal tuberosity; Ig, ligament of
the patella cut off; tb, tubercle.

the femur. In most Perissodactyla and Rodentia, and in
some Insectivora and a few fossil Carnivora, a third trochanter
is present.

78 ELEMENTS OF MAMMALIAN ANATOMY

The patella, or knee-cap (Fig. 22), is a sesamoid bone de-
veloped in the tendon of the quadriceps extensor muscle (Fig.
58). It is somewhat the shape of an almond and about half
its size. It articulates with the trochlea of the femur.

The tibia is the larger bone of the crus. It presents two
enlarged extremities and a shaft whose cross-section is tri-
angular. It articulates with the femur and fibula proximally
and the fibula and talus distally (Fig. 22). This is the longest
bone in the cat's skeleton. Between the concave condyles on
the proximal end is a notch giving attachment to the crucial
ligament of the knee-joint (Figs. 42, 47).

The prominences of the lateral and medial aspects of the
proximal extremity are the external and internal tuberosities
respectively. Beneath the former is the facet for articulation
with the fibula (Fig. 42). The tubercle, a prominence on the
cranial side of this extremity, is for the insertion of the liga-
mentum patellcB, which is really the termination of the tendon of
the quadriceps extensor muscle (Fig. 58). On the caudal
aspect between the condyles is the popliteal notch. The sharp
cranial border of the bone forms the crest. On the distal
extremity is a process, the internal malleolus, bearing two
grooves, the more caudal of w^hich shelters the tendon of the
flexor longus digitorum muscles while the other is for the tibialis
posticus (Fig. 58). A facet is present on the lateral aspect of
this extremity for articulation with the fibula.

The fibula in proportion to its length is the slenderest bone
in the skeleton. It is the outer or lateral bone of the crus, and
articulates proximately with the tibia and distally with the tibia
and talus (Fig. 22). The proximal extremity is the head, upon
which is a circular facet for articulation w^ith the tibia. The
sharp edge along the cranial aspect of the shaft furnishes
attachment to the interosseous membrane uniting the two bones
of the crus. The medial aspect of the distal extremity shows
a prominent facet for articulation with the talus. Immedi-
ately proximal to this is the articular surface for the tibia.

THE SKELETON

From the lateral aspect projects the external malleolus, on the
caudal side of which is a groove for the peroneus brevis muscle,
and on the cranial side is a slight depression for the peroneus
longus (Fig. 58).

In many of the Mammalia the two bones of the crus are more
or less united. In most of the Chiroptera
and Ungulata the hbula is rudimentary.
The middle portion of the fibula is ab-
sent in the horse and its distal portion
is fused with the tibia (Fig. 36). The
ancestor of the Equidae in Eocene times
had a well-developed fibula, but in the
evolution of the horse this bone has
gradually diminished in size^ as shown
in the figure.

The tarsus is composed of seven bones
in two rows. The proximal row contains
the OS calcis, talus, and navicular or
scaphoid; the distal row the cuboid, and
three cuneiform bones. The os calcis, or
calcaneum, is the largest bone of the
tarsus, being twice as long as broad (Fig.
44) . Its caudal end presents a groove for
the tendon of the plantaris muscle. The
peroneal tubercle is on the outer side of
the distal extremity. The sustentaculum
tali, a shelf-like process projecting from
near the middle of the inner side, sup-
ports a facet for the tendon of the flexor
longus digitorum muscle (Fig. 59).

The talus lies on the inner or medial
side of the calcaneum and articulates
with the tibia, fibula, calcaneum, and scaphoid. The bone is
composed of a body, neck, and head. The body is proximal
and bears a trochlear surface for articulation with the tibia.

OR
OF

Fig. 43. — Inner
Medial Aspect
Right Fibula.

a, Facet for tibia; or,
facet for talus; ex, ex-
ternal malleolus; h, head;
s, shaft; /, articular sur-
face for tibia; gr, groove
for peroneus longus
muscle.

ELEMENTS OF MAMMALIAN ANATOMY

The head bears a convex surface for articulation with the
navicular. The neck is the constricted portion between the
body and the head.

The scaphoid lies on the medial side of the foot and articu-
lates with the remaining six bones of
the tarsus. It may be recognized by
its deep concave surface for articula-
tion with the talus, and also by the
tuberosity, a process on its medial
plantar angle (Fig. 44).

The internal cuneiform is next to the
smallest bone of the tarsus. It articu-
lates with the navicular, middle cunei-
form, and first and second metatarsals.
The fuiddle cuneiform is a wedge-
shaped bone and the smallest element
of the tarsus. It articulates with the
other two cuneiforms, the scaphoid and
second metatarsal. The external cunei-
form may be recognized by a strong
hook-like process on its plantar surface.
It articulates with the scaphoid, mid-
dle cuneiform, cuboid, and second and
third metatarsals.

The cuboid is the lateral bone of the
distal row. It may be recognized by
the deep groove on its plantar surface
which shelters the tendon of the per-
oneus longus muscle.

The typical arrangement of the tar-
sal elements in vertebrates is similar to
that of the carpus. Three bones, a
tibiale, intermedium, and fibtdare, com-
pose the proximal row, while five tarsalia form the distal row.
The centrale occupies the center of the tarsal region. In the

Fig. 44. — Dorsal Aspect
OF Left Hind-foot.
ag, Talus; ar, articular
surface of the tibia; cb,
cuboid; ec, external cunei-
form; gr, groove for the ten-
don of the plantaris; h, head
of the fourth metatarsal; ic,
internal cuneiform; 7nc,
middle cuneiform; Wi, hal-
lux or first metatarsal; W2,
W3, ni4, and ws. second,
third, fourth, and fifth
metatarsals; nv, navicular
or scaphoid; oc, os calcis,
or calcaneum; 3, proximal
row of phalanges; .2, middle
row of phalanges; i, distal
row of phalanges.

THE SKELETON 8 I

adult mammal, fusion of some of these elements occurs, so
that not more than seven distinct bones are present in any
form. The talus contains the tibiale and intermedium, while
the fourth and fifth tarsalia form the cuboid.

The metatarsus consists of five bones, the first of which
is rudimentary, while the other four are longer than the meta-
carpus, which they resemble (Fig. 44). The first metatarsal
is smaller than any bone of the tarsus. It articulates with
the internal cuneiform and is also in contact with second
metatarsal. The four long metatarsals have a slight dorsal
convexity, each one consisting of a base or enlarged proximal
part, a shaft or middle portion, and a head or distal rounded
articular process. On the plantar surface of the head of each
metatarsal is a median spine, on each side of which is a con-
cavity for a sesamoid bone. These sesamoid bones are fre-
quently lost in cleaning the skeleton.

The number of functional metatarsals in mammals varies
from one to five. Usually the number of metacarpals and
metatarsals is the same, but in the tapir there are four meta-
carpals and but three metatarsals. All Monotremata, Car-
nivora, and Primates have five metatarsals, but in the cats,
dogs, and hyenas the first metatarsal is vestigial. In early
geological . times all mammals possessed five metatarsals, the
number of which in many cases has gradually diminished
owing to environment, as is shown in the phylogeny of the
horse (Fig. 36).

The Equidte possess but one functional metatarsal and two
rudimentary ones, although Orohippus, the ancestor of the
horse, had three functional metatarsals.

The phalanges of the cat's foot are twelve in number. Each
metatarsal except the first supports three phalanges. The
proximal phalanges are the stoutest, and the distal the smallest.
Each distal phalanx bears a claw.

In all five-toed animals, such as Primates, there are four-
teen phalanges, each digit being composed of three, except
the hallux, which has two.

82 ELEMENTS OF MAMMALIAN ANATOMY

LABORATORY STUDIES AND SUGGESTIONS

1. Describe the articulations of the innominate bone.

2. How do you distinguish the cranial from the caudal aspect of the os
innominatum?

3. \\ hich processes derive their names from their location?

4. Draw the lateral aspect of the os coxae and label all features.

5. Name the four parts of the bone in order of size.

C. What two orders of mammals have no pelvic limbs?

7. Describe what is seen in viewing the femur from the cranial aspect.

8. Name the processes of the femur.

9. Draw the distal aspect of the femur.

10. How do you distinguish the right from the left femur?

11. Describe the patella.

12. Draw the caudal aspect of the tibia and label all features.

13. How do you distinguish the right from the left tibia?

14. Describe the articulations of the fibula.

15. What features distinguish the proximal from the distal extremities of the
fibula?

16. Write 100 words describing the crus in other mammals than the cat.

17. Draw the ventral aspect of the tarsus and label all parts.

18. Which of the tarsals support metatarsals?

19. Name the tarsals in order of size.

20. Draw the lateral aspect of the third metatarsal.

21. How do you distinguish a metatarsal from a metacarpal?

22. How do you distinguish the proximal from the distal end of a metatarsal?

23. Describe the condition of the metatarsals in various mammals.

24. In most mammals how many phalanges to each digit?

25. What artiodactyls have you seen with only two functional digits on the
posterior limbs?

THE JOINTS

The study of the articulation of the bones and the ligaments
holding them in place is known as syndesmology. There are
three general classes of articulations: Synarthroses, or im-
movable joints; amphiarthroses, or joints with slight motion;
and diathroses, or joints freely movable. A synarthrodal
joint is exemplified in the sutures between the bones of the
skull. The two surfaces of bone are
separated by fibrous membrane only.
An amphiarthrodal articulation oc-
curs between the bodies of the ver-
tebrae and also in the union of the
sacrum with the ilium. In the ar-
ticulation of the vertebrae the con-
tiguous surfaces of the bone are
faced by flattened discs of iibro-
cartilage (Fig. 22).

The diarthrodal articulation is ex-
emplified in all joints allowing free
motion. Such joints are composed
of the following parts: the ends
of two bones having their contiguous surfaces covered
with cartilage; a synovial membrane forming a short tube
whose ends are closed by the cartilaginous articulating
surfaces; and several ligaments varying in number from two
or three to a dozen (Fig. 45). There are four kinds of the diar-
throsis: the arthrodia, or gliding joint, which occurs between
the bones of the carpus; the enarthrosis, or ball-and-socket
joint, such as at the hip or shoulder; the ginglymus, or hinge
joint, exemplified at the elbow and knee; and the rotatoria,
or pivot joint, formed by the articulation of the axis and atlas.

As the knee-joint can be readily dissected and the parts
well displayed; it is here described somewhat in detail. The

Fig. 45. — Diagram of a
Diarthrodal Joint.
ar, Articulatory cartilage;
Ig, ligament; sn, synovial mem-
brane; sy, synovial fluid in
synovial cavity; /, tibia; v,
femur.

ELEMENTS OF MAMMALIAN ANATOMY

leg should be detached at the hip-joint and the muscles largely
removed, taking care in the immediate neighborhood of
the knee that the ligaments are not cut. There are eight
ligaments to this joint. These may be classified into those

connected with the patella: the
capsular ligaments; the collat-
eral ligaments; the crucial liga-
ments; and the meniscal
ligaments (Fig. 46).

(i) The Ugamentum patcllce,
or anterior ligament, extending
from the patella to the anterior
tubercle on the tibia, is the
strongest ligament of the knee-
joint, and is really a continuation
of the tendon of the quadri-
ceps femoris muscle. (2) The
capsular ligament, which entirely
surrounds the joint except in

psular ligament cut and reflected ^ , oCCUpicd by the an-

mediad; bi, tendon of the popliteus '-^^'^ t' .

muscle pulled proximad to display tcrior and lateral ligaments, con-

sc; en, caudal projection of condyle . , r . , • / j

of tibia; ex, antero-external liga- SlStS of tWO partS, a mn/Za/ and

ment of the meniscus; ex, external ^ caildal pOrtioil. The former

lateral ligament; fb, fibula; fm, ^ • i r i

femur; ig, ligament of the quadri- is seen on either Side 01 the an-

ceps femoris muscle; pt, patella; , • liVqmpnt pxtendiuff from
se. external or lateral meniscus; sem, terior Ugamcni, exienuillg iruni

medial or internal meniscus, //, |-}^g femUr tO the tibia aS a thick

tibio-fibular ligament; tb, tibia. 1,11

membrane, and more laterally
being attached to the menisci. The caudal part extends from
the fabellie and the femur to the tibia and menisci. (3) The
collateral ligaments pass directly from the epicondyles of the
femur to the tibia or fibula, (a) The Ugamentum collateralc
Jibulare or external lateral ligafnent proceeds from the external
tuberosity of the femur to the head of the fibula, (b) The
Ugamentum collaterale tihiale or internal lateral ligament, much
shorter than the external one, extends from the internal tuber-

FiG. 46. — Lateral Aspect of Dis-
sected Knee-joint.
ad. Adipose tissue; ax, antero-in-
ternal ligament of the meniscus; ep,
capsular ligament cut and reflected

THE JOINTS

osity of the femur to the internal tuberosity of the tibia. The
anterior and capsular ligaments must be cut in order to see the
(4) crucial ligaments, which are short, and cross each other
in the region of the intercondylar
notch. The posterior crucial extends
from the caudal margin of the head
of the tibia to the mediocranial angle
of the intercondyloid notch of the
femur. The anterior crucial extends
from the summit of the tibia to the
caudolateral angle of the intercon-
dyloid notch. (5) The ligamenta
capituli fibulce. These are very
short, extending from the head of
the fibula to the outer tuberosity of
the tibia. In addition to these liga-
ments, there are (6) the ligaments
of the menisci, four bands uniting the

ment; ar, articular surface of
menisci to the bones. The menisci condyle of tibia; en, condyle

or semilunar cartilages are two bicon- of/^^J^^ cj capsular ligament

^ cut along the line Ig and re-

Cave cartilaginous plates, about one fleeted proximad; ex, external

.,1. . ,1 • 1 • . 11. lateral ligament; /6, fibula; /w,

millimeter thick, interposed between femur; in, internal lateral liga-

the condyles of the femur and tibia. ??^"^' ^^' ^^^ ^"^^^ ^.^ capsular

ligament; pc, posterior crucial
The synovial membrane is a very ligament; pi, posterior external

thin transparent sheet lying within ^'^""^"^' °^ '^' meniscus; sm.

Fig. 47. — Caudal Aspect
Knee-joint with Cap-
sular Ligament Cut.

ac. Anterior crucial liga-

the capsular sheath of the joint.

medial or internal meniscus;

Jl^ snie, lateral or internal menis-

, , , • r ^'^^i ^f' liga^nients of the head

secretes the white glairy synovia for of the fibula; tb, tibia.
lubricating the joint. The synovial

fluid and membrane may be demonstrated by cutting open a
fresh joint obtained from the butcher-shop (Fig. 45).

All other freely movable joints are similar in structure to
the knee-joint, but have no menisci and fewer ligaments.
The shoulder-joint has only two or three ligaments, the most
important of which is the capsular. The elbow-joint has

86 ELEMENTS OF MAMMALIAN ANATOMY

four ligaments and the hip-joint only two. In the ankle-
joint there are eight ligaments in addition to the capsular.

These ligaments which bind the joints consist of white
fibrous connective tissue which under the microscope is seen
to be composed of parallel and interlacing fibers. They are
very tough and have but little elasticity, so that the joints are
seldom dislocated.

LABORATORY STUDIES AND SUGGESTIONS

1. Give three examples of each of the three general classes of joints.

2. Explain difference in anatomy of the three classes of joints.

3. Without aid of the microscope can you detect any differences between a
ligament and a tendon?

4. By removing the capsular ligament describe the ligaments that can be
displayed on the lateral and caudal aspects of the knee-joint.

5. After bringing to view by dissection as many ligaments as possible on
inner aspect of knee-joint, draw and label all parts.

6. Draw the menisci.

7. By careful dissection note the ligaments present in the hip-joint.

8. How many ligaments can you find in the shoulder-joint?

9. In what joints is synovia present?

10. Cut a very thin slice of articular cartilage about a millimeter square,
mount in dilute acetic acid, and make drawing as seen under the microscope.

THE MUSCLES

The study of the muscular system is known as myology.
The muscles are of two kinds: voluntary, which are under the
control of the will; and involuntary, which cannot be controlled
by the will. All muscles moving the bones are voluntary and
are supplied with branches of the cerebrospinal nerves. Ex-
amples of involuntary muscles are found in the walls of the ali-
mentary canal, the ureter, bronchial tubes, and blood-vessels.
These are supplied with nerves from the sympathetic nervous
system (Fig. ii6). The structure of a voluntary muscle
may be seen by teasing a small piece on a slide in a drop of
water, covering with a cover-glass, and examining with the
compound microscope. It is composed of striated fibers from
one to fifteen centimeters in length, while involuntary muscle is
composed of cells more or less spindle-shaped and non-striated,
except in the heart (Figs. 8 and ii).

There are over five hundred voluntary muscles in the cat, each
of which is usually attached at either end to the periosteum of a
bone. The point of attachment on the unmoved bone is
known as the origin of the muscle. The insertion of a muscle
is its attachment to the bone which it moves. In the case of the
biceps, its origin is on the scapula and its insertion on the
radius. Usually a muscle originates and terminates in a
white glistening cord called a tendon, composed for the most
part of white fibrous tissue.

Each muscle-fiber is surrounded by a transparent elastic
sheath, the sarcolemnia. A number of libers bound together
by a loose connective tissue, and the whole enveloped by an
extension of the same, is a fasciculus. The tissue connecting
the fibers is the endomysium, while that enveloping the fasciculus
is the perimysium. A number of fasciculi bound together in
a sheath, the epimysium, constitutes the entire muscle. The

88 ELEMENTS OF MAMMALIAN ANATOMY

epimysium is merely a deflected portion of the sheath enveloping
the fasciculus. It is visible to the naked eye as a thin shining
sheath beneath the tougher fascia which covers the muscles and
binds them together. According to function, muscles are
spoken of as Jlcxors, extensors, adductors, abductors, rotators,
elevators, depressors and sphincters. K flexor muscle is one which
by its contraction bends a limb or any portion of it. An exten-
sor muscle is the antagonist of a flexor and serves to bring the
two long bones into line. An abductor muscle is the one inserted
on a long bone, which it draws laterad from the axis of the limb
or the sagittal plane of the body. An adductor muscle is the
antagonist of an abductor. The pectoral muscles are adductors
of the forelimb. A rotator muscle is one which produces more or
less of a rotatory motion in the bone upon which it is inserted.
A rotator muscle is exemplified in the obturators, which arise on
the innominate bone and are inserted in the digital fossa of the
femur. An elevator muscle is represented by the temporal,
extending from the temporal bone to the mandible, which it
elevates. A depressor muscle is the antagonist of an elevator.
The digastric is a depressor of the mandible. A sphincter
muscle is one surrounding an orifice which it closes by contrac-
tion. The orbicularis oris in the lips is an example.

Muscles are named according to their function, shape, or
part to which they are attached. Thus the sternomastoid
muscle arises on the sternum and is inserted on the mastoid
process of the skull. The latissimus dorsi is so named because
it is a very broad muscle (Fig. 48) and occupies the dorsal part
of the cat's body. The extensor communis digitorum muscle
signifies by its name that it is the common extensor of the digits.

DISSECTION OF THE MUSCLES

Since the other systems are of more importance from the
standpoint of comparative anatomy and physiology than the
muscular, only the more important muscles will be described.
Great care should be exercised in removing the skin of the

THE MUSCLES 89

cat, in order that such superficial muscles as the platysma
myoides on the neck and side of the face, and occipitofrontalis,
may not be cut away. The skin is attached to the under-
lying muscles by the superficial fascia, a fibrous areolar tissue,
which contains the subcutaneous fat more or less abundant
in all specimens. The deep fascia is the fibrous and membra-
nous layer of dense tissue lying close against the muscles and
dipping down between them. The stronger parts of this fascia
are called aponeuroses.

Directions for Dissection. — Dissection does not mean the
cutting up, but the intelligent separation of one organ from
another and the removing of known portions to study the
deeper structures more carefully. The muscles should not be
cut loose from their origin or insertion, but merely separated
from each other by cutting the deep fascia in the longitudinal
direction of the muscle. If it is necessary to remove a muscle
for displaying those beneath, it should be cut transversely in the
middle and the two parts reflected. No portion of a muscle
or other tissue should be removed without knowing what it
is and noticing carefully its relation to the surrounding parts.
The specimen under dissection should be securely nailed to
the tray so that the muscles are made tense. When the parts
become dry, they should be thoroughly wet with water. If
the formalin in which the specimen has been preserved is
irritating to the mucous membrane of the dissector, a half liter of
5% ammonium hydrate should be poured over the specimen.

In the following tables most of the important muscles of the
cat are arranged according to their location and ease in dissec-
tion. Perhaps no class will have time to dissect out all of the
muscles here described. In most cases only those of the fore-
limb with such others as the instructor may assign will be all
that the student will have time to study carefully. The more
ambitious in the class may wish to work out the posterior limb
and compare with the anterior. This is to be encouraged.
The origins and insertions are given only in a very general way,

90 ELEMENTS OF MAMMALIAN ANATOMY

Fig. 48. — Ventral Aspect of the Cranial Half of the Cat. The super-
ficial muscles have been removed from the left side and the scapula reflected
laterad to display the serratus and adjacent muscles.

a. Triceps; b, triceps; car, carotid artery; c, c\, and d, scalene muscles; cph,
cephalohumeral; ere, coracobrachialis; dg, digastric; ds, cut end of the digastric;
ext, external oblique; /, inferior constrictor; gh, geniohyoid; h, humerus; i, sca-
lene; ic, triangularis sterni; int. internal oblique; j, hyoglossus; k, styloglossus;
/, rectus lateralis; Id, latissimus dorsi reflected lateral and much of the reflected
portion cut off; Iv, levator scapulae; m, longus colli; man, mandible; mas,
masseter; mh, mylohyoid; md, median ventral line; n, facial aponeurosis of the
external oblique; pCi, PC2, pes, and pei, first, second, third and fourth parts of
the pectoralis muscle; pet, portion of the pectoral muscle of the left side; ret, left
rectus abdominalis; sh, sternohyoid; shi, sternohyoid of the left side with its
middle portion removed; std, sternothyroid; stfn, sternomastoid; st, portion of
left sternomastoid; sub, subscapularis; sps, suprascapularis; /, occipitoscapularis;
tm, teres major; /r, triceps; a;, cleidomastoid; i, 2, 3, 7, 8, and 9, ribs; 5, trachea.

THE MUSCLES

Fig. 48.

92 ELEMENTS OF MAMMALIAN ANATOM\

thus leaving to the student the pleasure of working out the
details. In general, the arrangement and descriptions follow
Reighard and Jennings very closely, however, in nearly every
case they have been verified by special dissections and in class
work. The student will be interested in finding many minor
variations which will add zest to the work. He should also note
carefully the muscles which together effect a certain motion,
such as the flexion of the forearm or the extension of the digits.

DESCRIPTION OF MUSCLES

The skin muscles are usually removed with the skin and are
rather difficult to study.

(i) Cutaneous maximus has its origin from the outer surface
of the latissimus dorsi; the bicipital arch in the axilla; the linea
alba and from the thorax; and is inserted onto the skin. It
covers almost the whole side and moves the skin.

(2) Platisma: from the middorsal line from occiput to first
thoracic vertebra, and from side of neck; to the skin and muscles
of face and neck. A thin muscle covering side of face and neck
and sometimes described as two muscles, the portion dorsal
to insertion in skin is known as the supercervicocutaneous and
the portion ventral to the insertion as the cervicofacial muscle.

MUSCLES OF THE SHOULDER REGION

These muscles of the forelimb (3-45) will usually be dissected
in a short course. The more difficult muscles of the hand may be
omitted except for students who have developed a careful tech-
nique. Drawings should be made during the progress of
dissection. The exact determination of origin and insertion
should be deferred until later in any case where it would injure
undissected parts.

(3) Spinotrapezius (Fig. 54) (Trapezius inferior); neural
spines of thoracic vertebra} to spine of scapula and adjacent
fascia; draws scapula upward and backward.

THE MUSCLES 93

(4) Acromiotrapezius (Fig. 54) (Trapezius superior) ; neural
spines of cervical vertebrae to spine of scapula; holds scapulae
together.

(5) Clavotrapezius (Fig. 54); occipital bone and fascia of
middorsal line of neck to clavicle; pulls scapula upward and
forward. This muscle continues to the humerus as the clavo-
brachial. Both together are frequently described as one muscle,
the cephalohiimcral or ccphalohrachial.

(6) Occipitoscapularis (Fig. 48, /) (Levator scapulae dorsalis
or Rhomboideus capitis); lambdoidal ridge to scapula; draws
scapula forward and rotates it.

(7) Rhomboideus (Fig. 54) (Rhomboideus major and minor
of man); spines of adjacent cervical and thoracic vertebrae to
scapula; draws scapulae dorsomediad.

(8) Levator scapulae ventralis (Fig. 54) (Levator claviculae) ;
atlas and basioccipital to metacromion and infraspinatus fossa;
pulls scapula craniad.

(9) Cleidomastoideus (Fig. 48) (clavicular portion of sterno-
cleidomastoid of man); mastoid process to clavicle; turns head
and depresses snout.

(10) Latissimus dorsi; (Fig. 54); neural spines from fourth
thoracic to sixth lumbar vertebrae to shaft of humerus; draws
arm dorsocaudad.

(11) Serratus anterior (Fig. 48) (Serratus magnus); first nine
or ten ribs to scapula; depressor of scapula.

(12) Levator scapulae (Fig. 48); last five cervical vertebra to
scapula; draws scapula cranio ven trad. Continuation forward
of serratus anterior and scarcely separable from it.

BREAST MUSCLES

(13) Pectoantibrachialis (Fig. 48); lateral surface of manu-
brium to superficial fascia of forearm near elbow; aids pectoralis
group and is the most superficial of this group.

(14) Pectoralis major (Fig. 48) (Ectopectoralis) ; two layers,
the superficial from manubrium and raphe anterior to it, the

94 ELEMENTS OF MAMMALIAN ANATOMY

deep layer from the ventral surface of manuljriuni and sternum;
both layers insert onto shaft of humerus.

(15) Pectoralis minor (Fig. 48) (Entopectoralis) ; sternum to
shaft of humerus.

(16) Xiphihumeralis (Fig. 48); Xiphoid process of sternum
to humerus. The pectoralis group of muscles draws the arm
mediad.

MUSCLES ON THE OUTER SURFACE OF THE SCAPULA

(17) Spinodeltoideus (Fig. 54) ; scapular spine to deltoid ridge
on humerus; flexor and rotator of humerus.

(18) Acromiodeltoideus (Fig. 54) ; acromion and metacromion
to humerus and on spinodeltoideus; flexor and rotator of
humerus.

(19) Clavobrachialis (Fig. 54); clavicle and raphe adjacent,
to ulna; continuation of clavo trapezius; flexor of antibrachium.

(20) Supraspinatus (Fig. 55); supraspinatus fossa to greater
tuberosity of humerus; extensor of humerus.

(21) Infraspinatus (Fig. 55); infraspinatus fossa to greater
tuberosity of humerus; rotator of humerus.

(22) Teres minor; glenoid border of scapula to proximal
end of humerus; rotator of humerus. Best studied after
removal of teres major, later.

MUSCLES ON THE INNER SURFACE OF SCAPULA

(23) Subscapularis (Fig. 48); subscapular fossa to lesser
tuberosity of humerus; pulls humerus mediad.

(24) Teres major (Fig. 56); glenoid border of scapula and
fascia with latissimus dorsi on humerus; rotator and flexor of
humerus.

(25) Coracobrachialis (Fig. 56); coracoid process to proximal
end of humerus; adductor of humerus.

MUSCLES OF THE UPPER ARM (BRACHIUM)

(26) Epitrochlearis (extensor antibrachii longus) ; latissimus
dorsi to olecranon process of ulna; extensor of arm and supina-
tor of hand.

THE MUSCLES . 95

(27) Biceps brachii (Fig. 57); bicipital tubercle of scapula to
proximal end of radius; flexor of arm and supinator of hand.

(28) Brachialis (Fig. 55); lateral surface of humerus to
proximal end of ulna; flexor of forearm.

(29) Triceps brachii (Figs. 54, 55); divisible into three
main portions:

(a) Caput later ale (Fig. 54) (Anconeus lateralis or ectotriceps) ;
proximal end of humerus to olecranon process of ulna.

{h) Caput longum (Fig. 54) (Anconeus longus or mediatri-
ceps); glenoid border of scapula to olecranon process of ulna.

{c) Caput mediale (Fig. 55) (en to triceps) ; consists of three
parts:

(x) Long portion (Anconeus posterior) ; shaft of humerus to
ulna.

(}') Intermediate portion (Anconeus internus); humerus to
olecranon.

(z) Short portion; supracondyloid bar to olecranon.
Triceps forms strong extensor of forearm; short portion alone
acts as supinator of hand.

(30) Anconeus ; distal portion of humerus to proximal end of
ulna; tensor of capsule of joint.

MUSCLES OF THE FOREARM (ANTIBRACHIUM)
SUPINATORS AND EXTENSORS

Note that the muscles of the forearm are covered by a tough
antrbrachial fascia which is made up of a superficial and a deep
layer. At the wrist the fascia becomes thickened to form, on
the ventral side, the transverse ligament, holding the flexor
tendons in place. On the fingers it forms tendinous sheaths
(vaginal ligaments) for the flexor muscles and ring-like annular
ligaments for the flexor tendons.

(31) Brachioradialis (Fig. 56) (supinator longus); from the
middle fifth of the humerus to the styloid process of the radius;
supinator of hand.

96 ELEMENTS OF MAMMALIAN ANATOMY

(32) Extensor carpi radialis longus (Fig. 56); lateral supra-
condyloid ridge of humerus to second metacarpal; extensor of
hand.

(33) Extensor carpi radialis brevis (Fig. 56) ; lateral supra-
condyloid ridge of humerus to third metacarpal; extensor of
hand.

(34) Extensor digitorum communis (Fig. 56) ; lateral supra-
condyloid ridge of humerus to phalanges of second, third, fourth
and lifth digits; extensor of four ulnar digits.

(35) Extensor digitorum lateralis (Fig. 55) (extensor digiti
quinti proprius of man) ; lateral supracondyloid ridge to dorsal
aspect of three or four lateral digits; extensor of three or four
ulnar digits.

(36) Extensor carpi ulnaris (Fig. 55); lateral condyle of
humerus to lateral aspect of fifth metacarpal; extensor of fifth
digit; largest extensor of the forearm.

(37) Extensor indicis {proprius) (Fig. 54) (includes ex. poUicis
longus); shaft of ulna to base of second phalanx of second digit;
extensor of second digit.

(38) Supinator (Hgaments of elbow joint to ventral surface of
radius) .

(39) Extensor brevis pollicis (Fig. 54) (ex. ossis metacarpi
pollicis; includes abductor longus poUicis of man) ; shaft of ulna
to base of first metacarpal; extensor and abductor of thumb.

FLEXORS AND PRONATORS OF FOREARM

(40) Pronator teres (Fig. 56) ; internal condyle of humerus to
cranial aspect of middle third of radius. Much of this muscle is
covered by those next described.

(41) Flexor carpi radialis (Fig. 56); internal condyle of
humerus to palmar aspect of proximal end of second and third
metacarpals; slender muscle flexing the hand.

(42) Palmaris longus (Fig. 56); internal epicondyle of
humerus to palmar fascia; flexor of first phalanx of each digit.

THE MUSCLES 97

(43) Flexor carpi ulnaris ; (Fig. 54) by two heads, one from
the medial epicondyle of humerus, the other from the medial
aspect of the olecranon to pisiform bone. The two heads are
separated by the ulnar nerve, but unite before reaching the
middle of the ulna. Flexor of hand.

(44) Flexor sublimis digitorum (or perforatus) (Fig. 56);
by two heads, one from the palmaris longus near the wrist, the
other from the flexor profundus digitorum; coalesce near
origin then sends tendons which are perforated by the flexor
profundus digitorum near their insertion onto the bases of the
second row of phalanges; flexor of the second phalanx of the
four ulnar digits.

(45) Flexor profundus digitorum (or perforans) ; (Fig. 56) five
heads which join at the wrist; first head from proximal end of
ulna; second head from medial epicondyle of humerus; third
and fourth heads from medial epicondyle; fifth head from ventral
surface of shaft of radius; the common tendon of the wrist
divides into five tendons, four of which perforate the tendons of
the sublimis at the bases of the first phalanges; to be inserted
in the base of the terminal phalanx of each digit. Flexor of all
digits.

(46) Pronator quadratus (Fig. 56); ventral surface of ulna
and adjacent interosseus membrane to ventral surface of radius;
pronator of hand.

MUSCLES OF HAND

For a more complete description the student is referred to
Reighard and Jennings.

(47) Lumbricales ; four small muscles in palm of hand from
the tendon of the flexor profundus to the radial side of the base
of first phalanx of the four ulnar digits; bends digits mediad.

(48) Abductor pollicis brevis (includes opponens poUicis of
man); transverse ligament on radial side of wrist to base of
phalanx of thumb; abducts thumb.

qS elements of mammalian anatomy

(49) Flexor brevis pollicis ; capitate (os magum) and scapo-
lunar bones to the first phalanx of thumb; flexor of thumb.

(50) Adductor pollicis; ventral surface of capitate to base
of first phalanx of thumb.

(5 1) Interossei ; small stout muscles between the metacarpals;
ventral of lateral surfaces of metacarpals to lateral surfaces of
first phalanges of the four ulnar digits. The second interosseus
is frequently called the flexor brevis digiti secundi (indicis).
Sometimes a second portion of the second interosseus is called
also the abductor digiti secundi.

(52) Adductor digiti secundi; ventral surface of capitate
bone to base of first phalanx of second digit.

(53) Abductor digiti quinti ; pisiform bone to first phalanx of
fifth digit.

(54) Flexor brevis digiti quinti ; ventral surface of fifth meta-
carpal to first phalanx of fifth digit. It is an interosseus of
the fifth.

(55) Opponens (adductor) digiti quinti; ventral surface of
capitate bone to radial surface of fifth metacarpal and base of
first phalanx.

MUSCLES OF THE POSTERIOR LIMB

If time permits it is advisable to dissect at least part of the
muscles of the hind limb and to compare where possible with
the muscles of the forelimb. It is well to note that the posterior
limb is much more closely fastened to the body than the forelimb
which makes it extremely difficult if not impossible to compare
the muscles of the shoulder and thigh. The student will, how-
ever, be interested in comparing the forearm with the shank.

LATERAL SURFACE OF HIP AND THIGH

Note the tough fascia lata covering the muscles of the thigh;
carefully dissect it away so as not to injure any of the underlying
muscles.

THE MUSCLES

Fig. 49. — Medial or Inner Aspect of the Hind Limb. {Drawn from
dissections made by Mr. Byerly).

Sartorius and gracilis muscles have been removed. Iliop., iliopsoas; P.,
plantaris; F.L.D., flexor longus digitorum.; E.L.D., tendon of extensor longus
digitorum.

lOO

ELEMENTS OF MAMMALIAN ANATOMY

Fig. 50.-LATERAL View of Hind Limb after Biceps, Tensor Fascia
Lata, and Caudofemoralis have been removed. {From dnsecUons made by

^Q.F.!'quadratus femoris; R.F., rectus femoris; o.l. obturator internis; Plant.
plantaris near origin.

THE MUSCLES

lOI

(56) Tensor fasciaelatae (Fig. 54) ; ventral border of ilium to
fascia lata.

(57) Biceps femoris (Fig. 54) ; tuberosity of ischium by apo-
neurosis to the cranial aspect of the tibia and on the patella;
abductor of thigh and flexor of shank; broad muscle on lateral
aspect of thigh.

Glut.Med.

Glut.Max.S^"/^^^

Fig. 51. — Lateral aspect of upper part of Hind Limb after Tensor
Fascia, Gluteus Medius, Gluteus Maximus, Caudofemoralis, Biceps,
Teniussimus, and the Great Sciatic Nerve Have Been Severed and
removed.

Ob. int., obturator internus; Q.F., quadratus femoris; Gi, gemellus internus;
Add. fern., adductor femoris; Tens., tenuissimus; Perif., pyriformis; Glut. Min.,
gluteus minimus with piece removed to show capsularis beneath. G.M., inser-
tion end of gluteus minimus; Getn. Sup., gemellus superior; Cap., capsularis; R.F.,
rectus femoris.

(58) Tenuissimus (abductor cruris); transverse process of
second caudal vertebra, becomes continuous with biceps femoris.

(59) Caudofemoralis (parameralis) (Fig. 50); transverse
processes of second and third caudal vertebrae to lateral border of
patella; abductor of thigh and flexor of shank.

(60) Gluteus maximus (Fig. 50), fascia and transverse
processes of last sacral and first caudal vertebrae to fascia lata
and greater trochanter of femur; abductor of thigh.

I02 ELEMENTS OF MAMMALIAN ANATOMY

(6i) Sartorius (Fig. 51); crest and ventral border of ilium to
ligament of petalla and adjacent crest of the tibia; abductor and
rotator of thigh and extensor of shank.

(62) Gluteus medius; ilium and fascia at root of tail to
greater trochanter of femur; abductor of thigh (Fig. 50).

(63) Pyrifonnis ; last two sacral and first caudal vertebriE to
greater tuberosity of femur; abductor of thigh (Fig. 51).

(64) Gemellus superior; dorsal border of ilium and ischium
to greater trochanter of femur; rotator and abductor of thigh.

(65) Gluteus minimus; ventral half of ilium to greater
trochanter of femur; rotator of thigh (Fig. 51).

(66) Obturator intemus; ischium to trochanteric fossa of
femur; abductor of thigh (Fig. 51).

(67) Gemellus inferior; lateral surface of ischium to inner
surface of the tendon of obturator internus and to capsule of
joint; abductor of thigh (Fig. 51).

(68) Gracilis (Fig. 57); ventral aspect of ischiopubal sym-
physis to shaft of tibia; adductor of thigh.

(69) Semitendinosus (Fig. 50) ; ischial tuberosity to the crest
of the tibia; flexor of shank; subcylindrical muscle of the inner
hamstring group.

(70) Semimembranosus (Figs. 49, 50); ischium to medial
epicondyle of femur and proximal end of tibia; extensor of
thigh; largest of inner hamstring group.

(71) Adductor femoris {magnus et brevis) (Figs. 49, 50);
ischiopubal symphysis to shaft of femur; extensor of thigh.

(72) Quadratus femoris; ischial tuberosity to great tro-
chanter and adjacent surface of lesser trochanter of femur;
extensor and rotator of thigh (Fig. 51).

(73) Obturator extemus; obturator foramen and adjacent
parts of pubis and ischium to trochanteric fossa of femur;
rotator and flexor of thigh (Fig. 50).

(74) Adductor longus (Fig. 49); cranial border of pubis to
middle of femur.

THE MUSCLES IO3

(75) Pectineus (Fig. 49); cranial border of pubis to shaft of
femur; adductor of thigh.

(76) Iliopsoas (Fig. 49); corresponds to human psoas and
iliacus; psoas portion arises by ten vertebral heads, the iliacus
portion from the ventral border of ilium; both parts converge
to insert in apex of lesser trochanter of femur; rotator and flexor
of thigh.

(77) Capsularis (gluteus qiiarttis, epimeralis); ilium to dorsal
surface of femur; rotator of thigh (Fig. 51).

(78) Quadriceps femoris ; consists of four muscles and may
be compared with triceps brachii of forelimb.

(a) Rectus femoris (Figs. 57, 5^); ilium near acetabulum to
outer, proximal surface of patella.

(b) Vastus lateralis (Figs. 50, 51) ; great trochanter and surface
of femur to outer, lateral surface of patella.

{d) Vastus intermedius; dorsal surface of femur to capsule
of joint. Entire group acts as extensor of shank; the inter-
medius alone acts as tensor of capsule.

MUSCLES OF SHANK OR LOWER LEG

(79) Gastrocnemius (Figs. 49, 50) arises by two heads;
caput laterale has four origins: (a) superficial fascia; (h) lateral
sesamoid bone of femur; {c) tendon of plantaris; {d) aponeurosis
covering plantaris; caput mediate from medial sesamoid bone
of femur and surface of femur; both heads unite in a tendon
which forms part of the tendon of Achilles and inserts onto the
proximal end of the calcaneus; extensor of foot.

(80) Plantaris (Figs. 50, 58), lateral border of patella and
lateral sesamoid bone to the plantar aponeurosis which gives
origin to the flexor brevis digitorum; flexor of digits. Its tendon
passes down through a sheath formed by the gastrocnemius
and soleus and over the insertion of the tendon of Achilles
(tendo calcaneus).

I04 ELEMENTS OF MAMMALIAN ANATOMY

(8i) Flexor brevis digitorum (Fig. 52) {pedis perforaius);
continuation of tendon of plantaris to base of second phalanges;
each tendon is spHt at the proximal phalanx to transmit a
tendon of the flexor longus digitorum; flexor of second phalanges
of digits.

(82) Soleus (Figs. 50, 59); lateral surface of head and ventral
surface of fibula to tuberosity of os calcis; helps to form the
tendon of Achilles (tendo calcaneus) and the sheath for the
tendon of the plantaris; extensor of foot.

(83) Popliteus (Fig. 49); lateral epicondyle of femur to
proximal end of ventral surface of tibia; rotator of thigh.

It will be necessary to remove the deep crural fascia from the
ventral surface of the shank in order to study the following
three muscles.

(84) Flexor longus hallucis (Fig. 59); from crural fascia,
ventral surface of tibia, medial surface and head of fibula to
bases of the terminal phalanges; the four tendons perforate the
four tendons of the flexor brevis; flexor of phalanges.

(85) Flexor longus digitorum (Fig. 59) ; mediocaudal surface
of middle third of tibia and head of fibula to join with tendon of
flexor hallucis longus.

(86) Tibialis posterior ; from caudal aspect of proximal third
of tibia and head of fibula to plantar surface of internal cunei-
form; extensor of foot.

MUSCLES OF DORSAL AND LATERAL SURFACES

OF SHANK

(87) Peroneus longus (Fig. 52); head and shaft of fibula to
bases of fifth and first metatarsals and slender branches to
other metatarsals; flexor of foot.

(88) Peroneus brevis (Fig. 53) ; lateral surface of distal half of
fibula to base of fifth metatarsal; extensor of foot.

(89) Peroneus tertius (Fig. 53); lateral surface of proximal
half of fibula to lateral border of extensor tendon of fifth digit;
extensor and abductor of fifth digit, and flexor of foot.

THE MUSCLES I05

(90) Extensor digitorum longus (Fig. 50); lateral epicondyle
of femur with four tendons to dorsal aspect of digits; extensor
of phalanges.

(91) Tibialis anterior (Fig. 50); lateral Surface of tibia, and
shaft and head of hbula to outer surface of first metatarsal;
flexor of foot.

MUSCLES OF FOOT

(92) Extensor brevis digitorum (Fig. 52); calcaneal ligament
and three metatarsals to proximal phalanges with tendon of
extensor longus.

(93) Quadratus plantae (plantar head of flexor longus
digitorum); lateral surface of calcaneus and cuboid to outer
surface of flexor longus digitorum; holds flexor digitorum
tendon in place (Fig. 53).

(94) Lubricales ; six muscles from flexor longus digitorum
to medial side of first phalanges of outer three digits; moves
these digits mediad (Fig. 53).

(95) Interossei; the interosseus muscle of the second digit
has five parts, three of which act as abductors of the second
digit and are known as ahdilctor longus, brevis, and intermediur
digiti secundi, respectively; the fourth is an adductor, adductos
longus digiti secundi; and the fifth is the adductor medius
digiti secundi; the interossei of the third and fourth digits are
alike and divide into two parts forming middle and long abduc-
tors and abductors digiti tertii and quarti.

There are five short muscles connected with the fifth digit:

(Fig. 53)-

(96) Abductor medius digiti quinti ; calcaneus and metatarsal
to first phalanx.

(97) Adductor medius digiti quinti; cuboid to first phalanx.

(98) Opponens digiti quinti; ligament of peroneal canal to
fifth metatarsal.

(99) Abductor digiti quinti brevis; ligament of peroneal canal
to lateral sesamoid.

(100) Adductor digiti quinti longus; lig. of peroneal canal
to tendon of extensor.

io6

ELEMENTS OF MAMMALIAN ANATOMY

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THE MUSCLES 107

MUSCLES OF TARSUS

(loi) Calcaneometatarsalis (part of adductor digiti quinti);
calcaneus to metatarsal, cuboid.

(102) Scaphocuneiformis ; scaphoid to cuneiform.

The student may now pass by the following muscles to those
of the body wall, omitting (102-175).

SUPERFICIAL MUSCLES OF HEAD AND FACE

(The following muscles will not usually be dissected.)

(104) Intermedius scutulorum, between scutiform cartilages;
draws ears dorsmediad.

(105) Corrugator super cilii medialis, midline of head to
upper eyelid; raises eyelid.

(106) Orbicularis oculi, frontal processes of maxillary, upper
and lower parts joined by tendon-fibers at outer angle of eye;
closes eye.

(107) Corrugator super cilii lateralis, ear to caudolateral
border of eye; pulls angle of eye caudad and ear forward.

(108) Frontoauricularis (Fig. 54) (if present), upper eyelid
to auricular cartilage.

(109) Levator auris longus, (Fig. 54), atlas and sagittal crest
to scutiform cartilage and to auricle. Pulls ear dorsocaudad.
(part of auricularis posterior of man).

(no) Auricularis superior (Fig. 54) (Attollens auris), sagittal
crest to auricular cartilage. Pulls ear dorsad.

(in) Abductor auris longus (part of auricularis posterior of
man) sagittal crest to eminentia conchae. Pulls ear caudad.

(112) Abductor auris brevis, lambdoidal crest to concha.
Pulls concha caudad.

(113) Epicranius (occipitofrontalis) Occipital portion from
sagittal crest, joins levator auris longus to form a tendinous
sheath, the galea aponeurotica, which covers skull between ears
and eyes and gives origin to the frontalis portion to be inserted
into the integument near the tip of the nose. It moves the
skin of nose and head.

Io8 ELEMENTS OF MAMMALIAN ANATOMY

(114) Zygomaticus (major), angle of mouth to scutiform
cartilage of ear; jnills angle of mouth dorsocaudad and ear
vetrocraniad.

(115) Submentalls, ventral midline to be inserted with
zygomaticus; draws ear ventrad.

(116) Depressor conchcc, ventral surface of neck to summit of
antitragus; draws ear ventrad.

(117) Frontoscutilaris, frontal bone to scutiform cartilage;
draws ear craniad.

(118) Adductor atiris inferior (part of auricularis anterior of
man), between zygomatic process of frontal bone and frontal
process of malar; draws ear craniodorsad.

(119) Tragicus lateralis; mandible to tragus; pulls ear ven-
trad.

(120) Rotator auris (scutuloauricularis inferior) scutiform
cartilage to eminentia conchie; rotates ear mediad and caudad.

(121) Adductor auris superior (part of auricularis anterior of
man), scutiform cartilage to spina helicis draws auricle craniad.

(122) Adductor auris medius (part of auricularis anterior of
man), scutiform cartilage to tragus; draws concha dorso-

craniad.

(123) Transversus auriculce, concha to auricular cartilage;

enlarges opening of ear.

(124) Auricularis externus, eminentia concha to auricular
cartilage; flexes auricular cartilage.

(125) Helicis, median surface of concha to auricular cartilage;
pulls cranial margin of concha proximad.

(126) Mandibuloauricularis (maxilloauriculare) mandible to
auricular cartilage. (Described in Anatomischer Anzeiger No.

56 page 57.)

(127) Antitragus, antitragus to tragus; constrictor of auditory

opening.

(128) Tragicus medialis, tragus to concha; Flexes concha.

(129) ConchcBUS externus, bridges a shallow gap in choncha;
constricts concha.

THE MUSCLES IO9

(130) Tensor lympani, small fossa in petrous bone to malleus.

(131) Stapedius, lateral surface of petrous bone to head of
stapes.

(132) Orbicularis oris, concentric subcutaneous fibres around
the mouth.

(133) Zygomaiicus minor (malaris) if present — ventral side of
eye to angle of mouth.

(134) Quadratus lahii superior is, may be distinguished in
two parts:

(134 a) Levator lahii superioris alaeque nasi, on side of nose,
and

(134 b) Levator labii superioris proprius (or caput angulare)
or larger portion. Erects whiskers and . raises upper lip.

(135) Caninus (levator anguli oris); retracts whiskers and
raises upper lip.

(136) Buccinator, beneath caninus; raises upper lip.

(137) Myrtiformis (nasalis of man in part); dilator of nares
and elevator of upper lip.

(138) M oils tackier (incisivi of man) in upper lip; carries Hp
craniad.

(139) Quadratus labii inferiores, in lower lip, not constant,
depresses lip.

(140) Transversus menti, usually not present, from cranial
portion of alveolar border of mandible to join in midline with
corresponding fibres from opposite side.

DEEP MUSCLES OF HEAD AND NECK

(145) Sternomastoid (sternal portion of sternocleidomastoid
of man), cranial end of manubrium to lambdoidal ridge; turns
head and depresses snout.

(146) Sternohyoid, first costal cartilage to body of hyoid;
draws hyoid backward.

(147) Sternothyrcoid, first costal cartilage to thyreoid car-
tilage; draws larynx backward.

no ELEMENTS OF MAMMALIAN ANATOMY

(148) Stylohyoid, stylohyal bone to body of hyoid; elevates

hyoid.

(149) Digastric, jugular process of occipital to external
coronoid fossa; depressor of lower jaw.

(150) MyloJiyloid, mandible to median raphe from symphysis
to hyoid ; elevates floor of mouth.

(151) Geniohyoid mandible near symphysis to body of
hyoid; draws hyoid forward.

(152) Jugulohyoid, jugular process to stylohyoid; draws
hyoid backward.

(153) Ceratohyoid cranial horn of hyoid to caudal horn;
brings horns of hyoid together to bring body of hyoid forward.

(154) Masseter, divided into three layers;

(a) Superficial layer, malar bone to lateral margin of ventral
border of mandible.

(6) Middle layer, ventral border of malar bone to ventral
border of external coronoid fossa.

(155) Temporalis divided into two layers.

{a) Superficial layer, zygomatic process and temporal fascia
to outer surface of coronoid process.

(b) Deep layer, temporal fossa to inner surface of coronoid
process. Elevator of lower jaw.

(156) Pterygoideus externus (sphenomeniscus of Prentiss),
external pterygoid fossa to medial surface of mandible. Eleva-
tor of lower jaw.

(157) Pterygoideus internus, internal pterygoid fossa to
mandible; elevator of jaw.

MUSCLES OF TONGUE

(158) Styloglossus, mastoid process and adjacent parts to
tip of tongue; retracts and raises tongue.

(159) Genioglossus, symphysis of lower jaw to dorsal part of
tongue; draws root of tongue forward and tip backward.

(160) Hyloglossus, body of hyoid bone to integument of
tongue; retracts and depresses tongue.

THE MUSCLES III

MUSCLES OF PHARYNX

(i6i) Tensor veli palatini, sphenoid to aponeurosus of roof of
mouth.

(162) Levator veli palatini, sphenoid to velum palatum.

(163) Glossopharyngeus, fibres from genioglossus and stylo-
glossus to the medial dorsal raphe of pharynx; constrictor of
pharynx.

(164) Constrictor pharyngis inferior, lateral surfaces of
thyreoid and cricoid cartilages to median dorsal raphe of
pharynx.

(165) Constrictor pharyngis medius, horns of hyoid to median
dorsal raphe of pharynx.

(166) Stylo pharyngeiis, mastoid process of temporal to middle
and superior constrictors. Constrictor.

(167) Constrictor pharyngis superior (pterygopharyngeus) .
Hamular process to dorsal raphe of pharynx.

MUSCLES OF LARYNX

(168) Thyreohyoideus, caudal border of thyreoid cartilage
to caudal horn of hyoid. Elevator of larynx.

(169) Cricothyreoideus, cricoid cartilage to thyreoid cartilage.

(170) Cricoarytenoideus, cricoid cartilage to arytenoid car-
tilage.

(171) Arytenoideiis transversiis, between caudal ends of
aryten d cartilages.

(172) Glossoepiglotticus, median septum of tongue to dorsal
surface of epiglottic cartilage. Draws epiglottis forward.

(173) Hyoepiglotticns, cranial surface of hyoid to epiglottic
cartilage.

(174) Tkyreoarytenoideus, thyreoid cartilage to arytenoid
cartilage; closes glottis.

(175) Cricoarytenoideus lateralis, cranial border of cricoid to
laterocaudal angle of arytenoid cartilage. Closes glottis.

112 ELEMENTS OF MAMMALIAN ANATOMY

MUSCLES OF THE BODY WALL

(176) Scalenus, divisible into several parts which may be
described as separate muscles.

(a) Scalenus mcdius, sixth to ninth ri])s to join rest of muscle
near first rib.

(/)) Scalenus posterior, third or fourth rib, joins rest of muscle
as (a).

(c) Scalenus anterior, second and third ribs, joins either
portions of muscle near first rib and the entire muscle is inserted
into the transverse processes of all cervical vertebrae. Flexes
neck and draws ribs forward.

(177) Transversus costarum {stemocosialis externus) , sternum
to first rib; draws sternum forward.

(178) Seratus posterior superior, first nine ribs to dorsal
medial raphe from the atlas to the tenth thoracic vertebra;
draws ribs forward.

(179) Serratus posterior inferior, last four or five ribs to
lumbar spinous processes; draws ribs forward.

(180) External oblique, last nine or ten ribs and lumbodorsal
aponeurosis to the median ventral raphe and linea alba from
the seventh costal cartilage to the pubic tubercle; constrictor
of abdomen.

(181) Internal oblique, lumbar aponeurosis from fourth to
seventh lumbar vertebrae, aponeurosis from ventral half of iliac
crest, and the three crural arches to the ventral midline; com-
pressor of abdomen.

(182) Transverse abdominal, false and floating ribs, trans-
verse processes of lumbar vertebrae, ilium, and crural arches to
linea alba; constrictor.

(183) Rectus abdominis, tubercle of pubis to first and second
costal cartilages and sternum; retracts ribs and sternum and
compresses abdomen. .

(184) External intercostals, between ribs in intercostal spaces;
protractors.

THE MUSCLES II3

(185) Internal intercostals, between ribs; retractors of the
ribs.

(186) Transverse thoracic {triangularis stcrni; siernocostalis
internus), sternum to cartilages of ribs and fascia covering
internal intercostals;

DEEP MUSCLES IN NECK VENTRAL TO VERTEBRAL

COLUMN

(187) Longus capitis (rectus capitis anterior major) second to
sixth cervical vertebrae to basioccipital and basisphenoid ;
depresses snout.

(188) Longus coli, a number of separate bundles of which
the thoracic group arise from the first six thoracic vertebrae
and are inserted into the costal process of the sixth cervical
vertebra; and the cervical group arises from the cervical vertebrae
and are inserted further forward in the midline of the centra;
bends the neck.

(189) Rectus capitis anterior minor, atlas to basioccipital;
depresses snout.

(190) Obliquus capitis superior, atlas to mastoid process;
turns head laterally.

(191) Rectus capitis lateralis, atlas to external surface of
jugular process; flexes head laterally.

MUSCLES OF THE VERTEBRAL COLUMN (BODY

REGION)

(192) Longissimus dorsi, median division connects spinous
process of vertebrae with accessory and mamillary processes of
other vertebrae in lumbar and thoracic regions; the lateral
division arises from the ilium and lumbodorsal fascia and are
inserted into the transverse processes of the lumbar, thoracic
and cervical vertebrae. In the thoracic region the spinalis
dorsi separates off. The cervical portion is sometimes distin-
guished as the longissimus cervicis; and the cranial portion as the
longissimus capitis. Extensor of vertebral column.

114 ELEMENTS OF MAMMALIAN ANATOMY

(193) Extensor caudae lateralis, sacral and caudal vertebrae to
dorsal surface of caudal vertebrae; raises tail.

(194) Iliocostalis, from the longissimus dorsi and ribs to
ventrolateral surface of ribs; draws ribs together.

(195) Splenius, cervical ligament and fascia of deep muscles
to lambdoidal ridge; lateral flexor of head; both acting together
elevates head.

(196) Longissimus capitis (trachelomastoideus) , last four
cervical vertebrie to mastoid process; lateral flexor of head.

(197) Spinalis dorsi, tenth to thirteenth thoracic vertebrae
to first nine or ten thoracic vertebrae and cervical forward
to second; extensor of vertebral column.

(198) Biventer cervicis (medial portion of semis pinalis
cervicis et capitis), aponeurotic arches of last cervical and first
three thoracic vertebrae to lambdoidal crest; raises snout.

(199) Complexus (lateral portion of semis pinalis cervicis
et capitis), closely associated with biventer cervicis; raises head.

(200) Longus atlantis, a portion of longissimus dorsi from
third cer\dcal vertebrae to wing of atlas; extends neck and draws
head laterad.

(201) Multifidus spinas, from transverse processes to spinous
processes craniad; extends back when both sides act; turns
vertebral column laterad when one side acts alone.

(202) Extensor caudae medialis, caudal extension of multi-
fiduous spinae; raises tail.

(203) Semispinalis cervicis, cervical portion of multifidus;
extends neck.

(204) Interspinales, between spinous processes.

(205) Intertransversarii, between transverse processes of
vertebrae.

(207) Rectus capitis posterior major, crest of axis (epistro-
pheus) to lambdoidal crest; raises snout.

(208) Obliquus superior, lateral border of transverse process
of axis to mastoid process; flexes head laterally.

(209) Obliquus capitis inferior, lateral surface of spine of
axis to transverse process of atlas; rotates head.

THE MUSCLES I15

(210) Rectus capitis posterior medius, cranial end of axial
spine to occipital bone; raises snout.

(211) Rectus capitis posterior minor, dorsal arch of atlas to
occipital bone; raises snout.

(212) Levator costarum, transverse processes -of thoracic
vertebrae to angle of rib caudad of origin; continuous with
external intercostals; pulls ribs dorsocraniad.

MUSCLES VENTRAL TO VERTEBRAL COLUMN

(213) Diaphragm, muscle fibres run radially from wall to
central (semilunar) tendon; the vertebral portion of the muscular
part arises from the second to fourth lumbar vertebrae, while
the sternocostal part arises from the xiphoid process and the
last five ribs.

(214) Psoas minor, last one or two thoracic and first three
of four lumbar vertebrae to the iliopectineal line craniad of
acetabulum; flexes back.

(215) Quadratus lumborum, last tw^o thoracic vertebrae
and last rib to anterior inferior spine of ilium, rests on ventral
surface of transverse processes of lumbar vertebrae; bends
vertebral column sideways.

(216) Iliocaudalis, ventral half of medial surface of ilium of
caudal vertebra. Flexor of tail.

(217) Levator ani (pubiocaudalis) symphysis of pelvis to
third, fourth and fifth caudal vertebrae. Frequently continuous
with iliocaudalis. Flexor of tail and compresses rectum.

(218) Abductor caudae internus {Coccygeus) spine of ischium
to second, third and fourth caudal vertebrae. Flexor of tail.

(219) Flexor caudae longus, last lumbar vertebra, sacrum
and caudal vertebrae to ventral surface of tail; flexor of tail.

(220) Flexor caudae brevis, first seven or eight caudal verte-
brae to ventral surface of caudal vertebrae as far back as the
tenth; flexor of tail.

(221) Abductor caudae externus (coccigis) dorsal border of
ilium and dorsal surface of sucrum to caudal vertebrae back
to eight or ninth. Bends tail sideways.

ii6

ELEMENTS OF MAMMALIAN ANATOMY

o
1-1

THE MUSCLES II7

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Il8 f^ ELEMENTS OF MAMMALIAN ANATOMY

Fig. 55.

THE MUSCLES II9

Fig. 55.

Fig. 55. — Lateral or Outer Aspect of Muscles of the Pectoral Limb.
a. Cranial part of the ento-triceps; a7i, annular ligament; aw, abductor digiti
quinti; c, extensor carpi radialis brevis; del, acromiodeltoid; dl, biceps; ecd, ex-
tensor communis digitorum; ecrl, extensor carpi radialis longus, whose tendon is
marked w; emd, extensor digitorum lateralis; ei, extensor indicis; exul, extensor
carpi ulnaris; eom, extensor brevis pollicis; ex, ulnar head of the flexor carpi
ulnaris; fu, flexor profundus digitorum; hu, humerus; i, caudal part of the ento-
triceps; o, olecranon process of the ulna; ^, claw of first digit; ^ec^, portion of
the pectoralis; r, region of the head of the radius; 5/), spine of the scapula; sh,
supinator longus; tri, ecto-triceps (caput laterale of triceps brachii) with its mid-
dle portion cut out.

120

ELEMENTS OF MAMMALIAN ANATOMY

Fig. s6.

THE MUSCLES 121

Fig. 56. — Medial or Inner Aspect of the Muscles of the Forelimb.
a, Supracondyloid ridge of humerus; ab, abductor pollicis; b, humerus; c,
humeral head of the flexor carpi ulnaris; cp, ento-triceps; d, insertion of a tendon
of flexor sublimis digitorum; e, ulnar head of flexor carpi ulnaris; eci, extensor
carpi radialis longus; ec2, extensor carpi radialis brevis; /, portion of the flexor
sublimis digitorum arising from the flexor profundvis digitorum; fs, the portion
of the flexor sublimis arising from the palmaris longus; pp, common tendon of
the flexor profundus digitorum; Jlx, flexor profundus digitorum; g, radial part of
flexor sublimis; tendon to second digit; h, flexor profundus digitorum; /, styloid
process of radius; k, pronator quadratus; /, flexor carpi radialis; o, short part of
the ento-triceps; ol, olecranon process; ot, tendinous loops; pect, pectoralis cut
off; pi, origin of the palmaris longus which is reflected caudad; pt, pronator teres;
r, ento-triceps; ro, coracobrachialis; s, split in the tendon of the flexor sublimis
revealed by cutting away the tendinous loop; ss, supraspinatus; si, supinator
longus; tm, teres major; tb, the head of the humerus; x, a tendon of the flexor
profundus digitorum whose portion between the two letters is cut out to dis-
play the insertion of d. (" Ecto-triceps" in figure should be "medi-triceps.")

122 ELEMENTS OF MAMMALIAN ANATOMY

Fig. 57. — Ventral Aspect of Muscles of Caudal Portion of Trunk and

Thigh.
a, Transversalis abdominis becoming aponeurotic; add, adductor femoris mag-
nus; c, pectineus; ex. oh, external oblique, whose aponeurosis on the left side is
removed;/, aponeurosis of external oblique; grc, gracilis with its middle part cut
out on the left side; m, median ventral line; ps, iliopsoas; p, penis; rcf, rectus
femoris; ret, rectus abdominis; sar, sartorius with its middle part cut out on the
left side; smh, semimembranosus; smt, semitendinosus; spmc, spermatic cord;
/, aponeurosis; trs, internal oblique with a rectangular piece cut out to show the
rectus and transversalis; ivg, tensor fasciae latae; is, testicle; vi, vastus medialis; x,
external abdominal ring.

Fig. 58. — Lateral Aspect of the Muscles of the Leg with the Glutei.

Tensor Vagin.e Femoris, Semitendinosus, and Biceps Femoris Removed.

a. Portion of semimembranosus; ah, adductor femoris magnus; h, peroneus ter-
tius; ct, cut surface of the vastus lateralis; d, peroneus brevis; eld, extensor longus
digitorum; gas, gastrocnemius; I, tendinous loop; Ip, annular ligament; It, external
lateral ligament of the knee-joint; Ig, tendon of the extensor longus digitorum; o,
tendinous arch of the peroneus longus; oc, os calcis; pi, peroneus longus; ret, rectus
femoris; t, ligamentum patella?; tr, greater trochanter; ts, soleus; tg, tendon of gas-
trocnemius; Ipl, tendon of the plantaris; th, tibialis anterior; vex, vastus lateralis
with a piece cut out.

THE MUSCLES

123

Fig. 57.

124 ELEMENTS OF MAMMALIAN ANATOMY

(222) Extensor caudae lateralis, sacral and caudal vertebra?
to dorsal surface of tail. Raises tail.

(223) Extensor caudae medialis, sacral and first caudal
vertebra' to dorsal surface of tail; raises tail.

(224) Sphincter ani externus with (225) Sphincter ani
internus form the constrictors of the anal pouch.

(226) Ischiocavernosus, ramus of ischium to outer surface
of crus penis. In female the insertion is at base of clitoris.

(227) Transversus perinei, medial surface of ischium to
join sphincter internus.

(228) Caudorcetalis, ventral surface of sixth and seventh
caudal vertebrae to spread over sides of rectum.

(229) Caudoanalis, ventral surface of second and third caudal
vertebrae to unite with sphincter ani internus; draws anus
craniodorsad.

MUSCLES OF UROGENITAL SYSTEM PECULIAR

TO MALE

(230) Levator scroti, sphincter ani internus to scrotum.

(231) Rectocavemosus {retractor penis) sphincter ani internus
to corpus cavernosum.

(232) Caudocavemosus, first two caudal vertebrae to corpus
cavernosum.

(233) Bulbocacemosus (accelerator nrince)

(234) Compressor urethrae membranaceae.

MUSCLES PECULIAR TO FEMALE

(235) Levator vulvae {constrictor cunni) homologous with
levator scroti of male.

(236) Constrictor vestibuli {rectovaginalis) sphincter internus
to urogenital sinus.

(237) Caudovaginalis, first two caudal vertebrae to base of
clitoris.

(238) Urethralis symphysis of ischium to sides of vagina
and urogenital sinus.

THE MUSCLES

12^

The muscles in the different orders of mammals have the
same general arrangement. Over four hundred muscles occur-
ring in the cat are found in man and have approximately
the same relative location and function, and the same nerve-
supply. The size and the shape of the muscles may vary
somewhat in accordance with the habits of
the animal. The pectoralis in the cat
consists of five parts, while in man there are
only two parts. The biceps is a simple
muscle in the cat, but in man it has two
well defined heads. The muscles for mov-
ing the ear, which are well developed in
the horse, cow, and cat, are exceedingly
rudimentary in man. The Cetacea and
Sirenia possess fewer muscles than the other
orders of mammals, as they have no hind-
limbs. These few remarks serve to show
that a familiarity with the muscles of any
one mammal guarantees a general knowl-
edge of the muscular system of all mammals.

m^Ji

If'

1/^

-ac

Fig. 59. — Caudal Aspect of the Muscles of the i

Crus and Foot with the Gastrocnemius, Soleus, \

AND Plantaris Removed. ah'

ad. Adductor; ac, tendon of Achilles; eg, external head
of gastrocnemius; fb, flexor brevis digitorum cut at x and
turned aside; /J, flexor longus digitorum;^, flexor longus
hallucis; i, peroneus longus; /, peroneus brevis; Ip, tendi-
nous loop through which pass the tendons of the flexor
brevis digitorum and the flexor longus digitorum; n, cut
tendons oi fb\ o, plantaris over the tuberosity of the os
calcis; p, tendon of the peroneus brevis; pi, tendon of the
plantaris, whose proximal portion is cut away; r, tendon
of the flexor longus digitorum pedis cut off as it passes
through the slit in the flexor brevis digitorum ; s, tendon fr~^^
of the flexor brevis digitorum split for the transmi^ion of i"* -'
the tendon of the flexor longus digitorum; so, soleus;
/, tendon of the flexor longus hallucis; x, plantaris giv-
ing origin to the flexor brevis digitorum.

fj>

126 ELEMENTS OF MAMMALIAN ANATOMY

LABORATORY STUDIES AND SUGGESTIONS

1. Describe the two kinds of muscles.

2. Draw a diagrammatic cross-section of the pal maris longus muscle repre-
senting the relation cf the fibers, fasciculi, sarcolcmma, endomysium, and
epimysium.

3. Describe an example of each class of muscles as to function.

4. Which muscles of the head and neck region derive their names from their
function?

5. Describe the chief muscles moving the mandible.

6. Describe the muscles lying ventral to the trachea.

7. Name three important muscles attaching the thoracic limb to the trunk.

8. Draw the caudal aspect of the triceps muscle.

9. What muscles flex the forearm on the arm?

10. Name the chief extensors and flexors of the digits.

11. On what process of the humerus do several of the flexors of the manus
arise?

12. On what process of the humerus do most of the extensors of the manus
arise?

13. Draw the outline of the ventral aspect of the flexor profundus digitorum
as it would appear detached from limb and with origins slightly separated.

14. Draw cranial aspect of the radius and mark the areas to which the muscles
are attached and the names of the same.

15. What muscles flex the manus on the forearm?

16. Describe the muscles extending the manus on the forearm.

17. What muscles in the forearm region derive their names from their function
and location?

18. Describe the large adductor of the thoracic limb.

19. Describe the muscles serving to move the humerus in four directions.

20. Describe the location and the use of the tendinous loops in the manus,

21. What muscles form the ventral and lateral walls of the abdomen?

22. Describe from your dissection four muscles causing the movement of the
ribs.

23. After removing the biceps femoris and sartorius, and dissecting the
muscles on the lateral aspect of the thigh, draw the muscles visible on the lateral
aspect, and label.

24. Name the muscles flexing the crus on the thigh.

25. Describe from your dissection the muscles extending the crus on the
thigh.

26. Describe the muscles forming the calf of the leg.

27. W^hat muscles are the opponents of the adductor magnus?

28. Draw the plantar aspect of pes showing the superficial muscles, and label
all the features.

29. Describe three muscles moving the digits.

30. Show by drawing the location of the muscles flexing the pes on the tibia
and label all the features.

ORGANS OF DIGESTION

A young lean cat which has had no food for twenty-four
hours is the best subject for the demonstration of the digestive
system. Directions for preparing the specimen are given in
the chapter on technique.

Fig. 6o. — Diagram of a Gland.

a, artery; v', vein; c, part of gland covered with capillaries; c, an acinus like c ,

cut open; i, duct.

The digestive system (Figs. 6i and 62) consists of the ali-
mentary canal and the accessory glands of digestion. The
canal is made up of the mouth, pharynx, esophagus, stomach,
small intestine, and large intestine. Its entire length is about
five times that of the cat from the tip of the nose to the root
of the tail. The accessory glands consist of five pairs of sali-
vary glands, the liver, and the pancreas. A gland is a tiny

127

128

ELEMENTS OF MAMMALIAN ANATOMY

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ORGANS OF DIGESTION 1 29

tube or collection of branching tubes which remove certain
materials from the blood and manufacture them into a fluid
useful to the body.

THE MOUTH

The mouth is bounded craniad by the lips, laterally by the
cheeks, and dorsally by the palate, where the mucous mem-
brane lies in seven or eight transverse ridges or ruga^, and
caudally depends from the palatine bones forming the velum
palati. To display the anatomy of the mouth, one should
remove the right half of the mandible. From either side
of the velum palati two folds of membrane diverge as they
extend to the floor of the mouth at the root of the tongue.
The cranial fold is the anterior pillar and the caudal one is the
posterior pillar of the fauces (Fig. 62). The caudal portion of
the mouth between these folds is known as the fauces. It
opens into the pharynx. On either side of the tongue between
the two pillars is a crescentic depression holding a tonsil. In
man, the tonsils sometimes become inflamed and enlarged,
giving rise to a disease called tonsillitis. The tonsil is a com-
pound lymphatic gland whose function is unknown.

Folds of mucous membrane called frena bind the lips to
the gums which are composed of dense fibrous tissue investing
the alveolar margins of the jaw-bones. The mucous lining
of the mouth contains many simple mucous glands invisible
to the naked eye. Those of the lips are called labial, of the
cheeks, buccal, and of the palate, palatine glands.

The tongue lying in the floor of the mouth is a muscular
mass composed of the geniohyoglossus, lingualis longitudinalis
superior and inferior, styloglossus, and hyoglossus muscles.
Caudally it is attached to the hyoid bone. Its investment
of mucous membrane is formed into a fold beneath it, called
the frenulum linguce. The dorsal surface of the tongue dis-
plays four kinds of papilla? (Fig. 62) : The vallate, numbering
from six to eight arranged in a V shape near the root; the flat,

I30

ELEMENTS OF MAMMALIAN ANATOMY

very numerous at the root; the conical, most numerous and
thickly set over the entire dorsal aspect; and the fungiform,

which are blunt and located
more thickly on the sides and
near the tip of the tongue
(Fig. 62).

The Teeth.^ During the
first year the cat develops
twenty-six teeth, known as
the deciduous or temporary
set, as they are later replaced
by a permanent set. The
three parts of a tooth are the
crown, neck, and fang (Fig.
64). The crown may be di-
vided into several portions
called cusps. A tooth split
longitudinally presents the fol-
lowing four features (Fig. 63) :
The enamel, a hard glistening
substance covering the entire
crown of the tooth down to
the neck; the cement, a bony
substance investing the fang;
the dentine, forming the interior

at, Arytenoia cartuage; aj, anrenor i •. ,• r a-U 4-^^4^U . ^»,J

pillar of the fauces; ... crico-epiglottic hard portlOU of the tOOth; and

ligament; cd, true vocal cords; cv, the /?w//? cai'//v, Containing in the

vallate papilla; ep, epiglottis; Jl, flat '

papilla; fg, fungiform papilla; fr, rCCCUt State the ncrVC- and

filiform papilla; g^ glottis; hy epiphyai bioQ^-vessels. The enamel con-

bone cut oii; ;, false vocal cord; ce,

lumen of the esophagus, which is cut sistS mOStly of the phosphatC of

off just as it opens into the pharynx; x^ • ^^i • i.* v,

pf, posterior pillar of the fauces; tn, hme. It IS the COVCrmg whlch

^o"s^i- when broken permits the tooth

to decay.
In an adult cat there are in each half of the upper jaw three
incisors, one canine, three premolars, and one molar (Fig. 64).

THE

Fig. 62. — Dorsal Aspect of
Tongue and Larynx.
at. Arytenoid cartilage; af, anterior

ORGANS OF DIGESTION 13I

In each half of the lower jaw there are three incisors, one
canine, two premolars, and one molar. The permanent denti-
tion of the cat is therefore expressed by the formula i M, c l{,
pm M, m Yi.

The upper incisor teeth are small and undivided both as to
root and crown. They are scarcely one-third as long as the
canine and are planted in the alveoli or sockets of the pre-
maxillary. The remaining teeth of this jaw are in the maxilla.
The canine or eye tooth is the longest and likewise is undivided
as to root and crown. The next three teeth are known as the
premolars. They vary much in size. The
anterior one is the smallest, being about the
size of the incisors. Its crown is usually
simple, although occasionally there is seen
a small posterior cusp, called triticone, in
distinction to the main cusp or protocone.
The root is usually composed of only one
fang. The second premolar is much larger Fig. 63.— Longitu-

° ^ ^ DiNAL Section of

than the first. Its crown presents a large the Canine Tooth.

T , i-i c, crown; cr, ce-

median cusp, or protocone; a very small ^^^t; d, dentine; e.
cusp, triticone, on the posterior side of the enamel; /, fang; m,

pulp-cavity; n. neck.

protocone half-way between its base and

apex; and a basal cusp, the talon, on the

posterior side of the base of the tooth. The prominent ridge

encircling the tooth at its base is the cingulum. The root is

composed of two fangs.

The third premolar or carnassial tooth is fully twice as large
as the second premolar. Its protocone is the large central
cusp, posterior to which is the large triticone. At the median
anterior angle is the deuterocone. The small projection at
the lateral anterior angle is the protostyle. The root of the
tooth usually consists of three fangs. The posterior tooth in
the maxilla is called the molar, since it is the only one not pre-
ceded by a milk tooth. It is very small and its crown presents
a grinding surface instead of a cutting one. Its root consists
of two fangs.

132 ELEMENTS OF MAMMALIAN ANATOMY

Each half of the mandible holds three incisors, one canine,
two premolars, and one molar. The incisors and canine are
so similar to the upper ones that they need no further descrip-
tion. The first premolar presents a princii)al cusp or proto-
conid, a lower small cusp or motaconid, and a projection, on

Fig. 64. — Lateral Aspect of the Permanent Dentition of the Cat.
i\, 12, 13, First, second, and third incisors of the uppet jaw; c, canine; pi. Pi,
and p3, first, second, and third premolars; m, molar; i, 2, 3, the incisors of the
lower jaw; 4, canine; 5 and 6, first and second premolars; 7, molar; c, cingulum;
d, deutrocone; m, metaconid; m, molar; pt, protoconid; re, protocone; td, talonid;
/, talon; tr, triticone.

the posterior side of the base, known as the talonid. A cingulum
or encircling ridge is also present at the base of the tooth.
The root consists of two fangs.

The second premolar is very similar to the first except that
it is larger and presents an anterior basal cusp in addition to
the others. The lower molar, sometimes called the sectorial,
because it shears against the upper sectorial or carnass al pre-
molar, presents two nearly equal cusps, the protoconid and
the paraconid. The root consists of two fangs, the anterior
of which is the larger. •

The deciduous or milk teeth begin to appear above the gums
when the kitten is two weeks old. The incisors and the canine
appear first, then second and third molars. The first upper
molars do not appear till the kitten is about six weeks old.
According to Jayne, the deciduous dentition is complete at

ORGANS OF DIGESTION 1 33

the end of the second month. At the end of the fourth month
the milk incisors are being displaced by the permanent teeth.
The formula for the temporary set is di J^, dc Jf , dm ^^.

Teeth are present in nearly all adult mammals. The whale-
bone whales, the duck-bill, and some of the ant-eaters have
no teeth in the adult state, but teeth are present during their
embryonic life. The Echidna shows no evidence of teeth at
any time. Most mammals have two distinct sets of teeth,
known as the milk or deciduous set, and the permanent set.
In the Marsupialia, the milk dentition is in a degenerate con-
dition. The milk teeth are present, but none become sufh-
ciently developed to appear above the gums, except the last
premolar, and in some cases the canine and the incisors. The
sloths have only one set of teeth and are therefore Monophy-
dont. Mammals having both a milk and a permanent set are
termed Diphydont.

In the majority of mammals the teeth are divided according
to form and function into four groups: incisors, canines, pre-
molars, and molars. Such a dentition is known as Heterodont,
in distinction to the Homodont dentition, in which all the teeth
have the same form, as is the case in the dolphins. In mam-
mals with a heterodont dentition the number of teeth in the
different genera varies considerably, as seen by the following
formula:

Pig iH,cH,pH,mH =44

Dog iH,c}i,p H,^H =42

Cat i ^, c H, P M, m K =3°

Porcupine \ }{, c %, p }{> ^ H = 20

Sheep i %,cH,p%,m% =32

Horse i H, c }i, p H, i^ H =44

Opossum i H, c Vi, p H, m ji = so

Man i M, c H, P %, m /i =32

The elephant presents a very specialized dentition. It has
no canines nor any lower incisors. The single pair of upper
incisors is developed into long tusks, much prized for ivory.
They continue to grow through out the entire life of the animal.

134 ELEMENTS OF MAMMALIAN ANATOMY

Six molars are present on each side, only one or two of which
are functional at once. The posterior ones move forward to
take the place of the anterior as these become worn out. The
tusks of the walrus are its canines greatly developed. None
of the typical modern Ruminants have upper incisors in the
adult state, though they are present in the embryo. Paleon-
tology has demonstrated that the ancestors of the Ruminants
had w^ell-developed upper incisors in the later Eocene times.
The occurrence of the rudimentary upper incisors in the embryo
furnishes evidence of a full dentition in the ancestors of the
ruminants, since the individual embryological history is some-
what of a recapitulation of the ancestral history of the race.

THE PHARYNX

The pharynx is that portion of the alimentary canal between
the mouth and the esophagus. The structure is well shown
by making a sagittal section through the head and neck. This
is best done with a saw, after the specimen is frozen by placing
it out-of-doors during one or two days of cold winter weather.

There are seven openings into the pharynx: The two pos-
terior nares (Fig. 19), opening anteriorly from the roof; audi-
tory or Eustachian tube on each side; the esophagus; and the
larynx, leading into the trachea. The mucous membrane lin-
ing the pharynx contains many simple microscopic mucous
glands.

VISCERA

The body cavity known as the celom must be opened before
the rest of the alimentary canal can be displayed. The entire
ventral wall of the thoracic and abdominal cavities should be
cut away with the bone forceps and scalpel. The body cavity
is divided into two parts by the diaphragm (Fig. 61). The
cranial portion, the thoracic cavity, contains the esophagus,
heart, blood-vessels, thoracic duct, trachea, and lungs. In the
young cat there is present also the thymus gland, stretching

ORGANS OF DIGESTION

135

craniad several centimeters from the base of the heart. The
transparent membrane lining this cavity and investing the
lungs is the pleura.

The caudal part of the celom is the abdominal cavity contain-
ing the abdominal viscera, which are here briefly described.

Fig. 65. — Viscera of the Human Body. (Deaver.)
CO, Colon; //, liver; lu, lung; si, small intestine; st, stomach.

The liver, a large brownish-red organ, is adjacent to the dia-
phragm on the right side, while the stomach (Fig. 61) lies close
to the diaphragm on the left. The spleen is the dark red, fiat,
elongated organ caudad of the stomach on the left side. The
sheet of thin transparent tissue more or less laden with

136 ELEMENTS OF MAMMALIAN ANATOMY

fat, depending from the stomach and covering the intestines
Hke an apron, is the greater omentum. It is a portion of the
peritoneum which Hncs the abdominal cavity and invests most
of the organs therein. The pancreas is a pinkish elongate
body, bent at a right angle near its middle, so that one portion
lies in the bend of the duodenum and the other dorsal to the
stomach. The kidneys may be recognized by their well-known
shape and dorsal location in the cranial lumbar region. The
ovaries are small pinkish bodies lying near the kidneys, adja-
cent to the dorsal abdominal wall. The uterus is easily known
by its two horns extending caudad from the ovaries to their
junction at the body of the uterus. The bladder, if full of
urine, is at once recognized; and if empty, appears as a small
hard pear-shaped mass ventrad to the rectum (Fig. 61).

ESOPHAGUS

The esophagus or gullet is that portion of the alimentary
canal leading from the pharynx to the stomach. In the thoracic
cavity it lies dorsal to the heart (Fig. 61) by the side of the
aorta. Immediately caudad of the diaphragm it opens into
the cardiac end of the stomach (Fig. 66).

STOMACH

The stomach is that dilated portion of the canal lying im-
mediately caudad of the diaphragm on the left side. The
esophageal end of the stomach is known as the cardiac portion,
and the intestinal end is the pyloric portion (Fig. 66). Here
a circular fold of mucous membrane embraced by a sphincter
muscle serves as a valve to open and close the pylorus or gate-
way to the intestine. The dorsal surface of the stomach is
its lesser curvature and the ventral convex surface is its greater
curvature. The structure of the walls of the stomach is
described below.

ORGANS OF DIGESTION

INTESTINE

137

The intestine is that much contorted portion of the canal
leading from the stomach to the external aperture or anus.
The first portion, the small intestine (Fig. 66), is about three

Fig. 66. — Ventral Aspect of the Alimentary Canal with the Ileum

Pulled to One Side.
ac. Small intestine opening into the large intestine; a, anus; ao, ascending
colon; hd, hepatic duct; ce, cecum; cd, cystic duct; cs, bile-cyst or gall-bladder;
cr, cardiac portion of the stomach; di, diaphragm; du, duodenum; do, caudal
part of the descending colon; dc, common bile duct; gc, greater curvature of the
stomach; //, ileum; j<?, jejunum; Ic, lesser curvature of the stomach; ce, esophagus;
pn, pancreas; py, pyloric portion; pa, mesenteric gland; pd, pancreatic duct;
r, rectum; sp, spleen; tc, transverse colon.

138

ELEMENTS OF MAMMALIAN ANATOMY

feet long in a largo cat, and is loss in diameter and much more
convoluted than the second portion, or large intestine.

Tho small intestine consists of three parts: the duodenum,
the jcjmi HDL and the ileum. The duodenum is the first twelve
or tifteen centimeters. A duct from the liver and the gall-
bladder and two ducts from the pancreas, empty into it. The

Fig. 67. — Transverse Section of the
Cat.
i. Sections of the intestine; d, duode-
num; a, aorta; pan, pancreas; pa, pan-
creas Aselli; spl, spleen; sp, spinous
process of the lumbar vertebra; tr,
transverse process; v, post-cava or in-
ferior vena cava; om, greater omentum;
the broken line is the peritoneum.

Fig. 68. — Cross-section of the
Cardiac End of the Stomach. X3.
cav. Cavity of the stomach; ex,
external muscular coat; in, internal
muscular coat; m, mucous coat; 7nm,
muscularis mucosa?; 5, submucous
or areolar coat; se, serous or peri-
toneal coat.

former is the common bile duct and the latter are the pancreatic
ducts. The jejunum is the portion of the small intestine next
to the duodenum. It is about twenty live centimeters long.
No special mark indicates its limits. It is so called because
that portion of the canal in man is frequently empty after
death. The ileum constitutes more than two-thirds of the small
intestine, is much convoluted, and extends from the jejunum
to the large intestine on the right side of the abdominal cavity,
near the iliac bone. The intestine is supported by the folds
of the peritoneum known as the mesenteries.

ORGANS OF DIGESTION

139

The large intestine consists of the cecum, colon, and rectum.
The cecum is the Ijlind conical projection at the beginning of
the large intestine. It is only one or two centimeters long.
There is no vermiform appendix in the
cat. The ileum opens into the large in-
testine at the junction of the cecum and
colon. An annular fold of mucous mem-
brane, strengthened by a sphincter muscle,
forms the ileocecal valve, which retains the
food in the small intestine until the
nutriment is absorbed (Fig. 66).

The colon, extending from the cecum
to the rectum, is composed of the as-
cending, transverse, and descending parts.
The ascending colon lies on the right
side, the transverse extends crosswise,
connecting the ascending with the descend-
ing, which lies on the left side. The de-
scending colon terminates in the rectum,
which is five or six centimeters long.

The waU of the alimentary canal is ^^^ ^^ _^ ^^^^^
composed of three chief coats — mucous, section of the Mucous

, , , Coat of the Stomach

areolar, and muscular, these coats may between the Lines a
be seen by cutting transversely, with a ^^d c in Fig 61 Shows

•^ ^ ^ -^ A Gastric Gland. X

sharp scalpel, a portion of the stomach 250. Diagrammatic.
hardened in formalin. The mucous coat giand;^rcoiumnaT'ep^
(Fig. 68) lines the lumen and contains thdiai ceils on the food

, > . surface of the stomach;

four typical structures: (a) an mner /, lumen of a gland; o.
epithelial layer, (b) a tunica propria sup- ^^^^^^^ ^'^ ^''^ ^^"•
porting (c) the secreting glands, and (d)
muscular layer — the muscularis mucosae — separating the
mucous from the submucous coat. The glands of the
mucosa vary much in the different portions of the canal.
The mucous coat of the esophagus of the cat is free
from glands, for the greater part, at least. In some animals

I40

ELEMENTS OF MAMMALIAN ANATOMY

like ihc (log, opossum, etc., esophageal glands are present
in the submucous coat. The function of these glands when
present is not exactly known (Goetsch Am. Jour. Anat.,
1910). The mucous coat of the stomach contains the gastric

Fig. 71a. — Diagram of a Small Cube Cut
FROM THE Wall of the Jejunum.

a. Artery; v, vein; ly, lymphatic; /, lacteal;
vi, villi; m, mouth of intestinal gland; i, in-
testinal gland of Lieberkiihn; 7nm, muscularis
mucos£e; sub, submucosa; cm, circular muscu-
lar coat; Im, longitudinal muscular coat.

Fig. 70. — Cross- sec-
tion of the Small In-
testine. X 5-

ex, Longitudinal mus-
cular coat; tn, circular
muscular coat; mu, mu-
cous coat; lb, glands of
Lieberkiihn; se, serous or
peritoneal coat; sm, sub-
mucous or areolar coat.

glands, which yield pepsin and hydrochloric acid, the chief
agents of the gastric digestive fluid (Fig. 69). The glands in
the cardiac end of the stomach differ from those in the pyloric
end in containing numerous parietal or acid cells which probably
secrete the hydrochloric acid for digestion.

ORGANS OF DIGESTION

141

Fig. yib. — Lacteals and Portal System of Dog.
a. Inferior mesenteric vein; b, gall-bladder; c, cecum; d, duodenum; e, esopha-
gus; i, parotid gland; j, jejunum; /, branches of portal vein in liver; lu, branches
of trachea and pulmonary artery in the lung; m, ilium; ol, colon; p, pancreas;
s, spleen; st, stomach; th. thoracic duct into which empty the white tubes, the
lacteals.

142 ELEMENTS OF MAMMALIAN ANATOMY

The mucous coal of the small intestine contains tube-like
glands, the intestinal glands of Licberkiihn, whose secretion
acts on the sugars, assists the pancreatic juice in the digestion
of proteins, and contains a hormone which plays an important
role in the control of pancreatic secretion. In the duodenum
and jejunum the mucous membrane is thrown into numerous
transverse folds, valvuli conniventes, which increase the surface
for absorption. The villi are minute finger-like processes (Fig.
70), barely apparent to" the naked eye, projecting into the
lumen for the purpose of absorbing the nutriment from the
chyle. They consist of a covering of columnar epithelial cells
(Fig. 71a), within which ends a chyle vessel or lacteal surrounded
by small blood-vessels held in place by connective tissue. The
fatty portions of the food are carried by the lacteals (Fig. 716) to
the left thoracic duct, and thence to the jugular vein, while
other portions of the food are taken up by the capillaries of
the portal system, which begin in the villi (Fig. 71a). The
mucous membrane of the large intestine likewise contains tube-
like glands similar to the intestinal glands, but no villi.

The submucous or areolar coat is adjacent to the mucous
coat of the intestine. It contains blood and lymphatic vessels,
nerve fibers and plexuses supplying the mucous coat. In cer-
tain regions of the digestive tube, as the duodenum and in
some mammals the esophagus, it also contains secreting glands
whole ducts penetrate the mucous coat and open upon the
epithelial surface. Next to the submucous coat is the muscular
coat, composed of tw^o layers, one of circular fibers, the other
of longitudinal fibers. An additional layer of oblique fibers
is present in the cardiac end of the stomach, which aid in
giving that organ the peculiar churning or peristaltic motion
necessary for chymification of the food. A fourth coat or
serous covering surrounds the muscular coat of the stomach
and intestines. It is merely a reflected portion of the perito-
neum which lines the entire abdominal cavity.

ORGANS OF DIGESTION

143

THE ACCESSORY GLANDS OF DIGESTION

• The salivary glands are five in number on each side of the
head. They secrete the saliva, of which certain elements have
the power of changing starch into sugar.

The parotid gland is the largest of the sahvary group and
lies just ventrad to the base of the external ear (Fig. 72)
beneath the skin. It is flat and about two centimeters in
diameter. Its secretion is poured into the mouth through the
parotid duct, (ductus parotideus stenonis), which may be seen
extending from the cranial mar-
gin of the gland over the masseter
muscle, to near the angle of the
mouth, where it perforates the
buccinator muscle, and opens
within the mouth on the cheek,
opposite the prominent cusp of
the last premolar. The duct
and gland may be injected
with Berlin blue by inserting
the cannula into the orifice of
the duct (Fig. 72).

The submaxillary gland is
near the angle of the mandible
and ventrad to the parotid. The submaxillary duct extends
from its anterior surface, between the digastric and masseter
muscles, to its orifice on the floor of the mouth, opposite the
last tooth of the mandible.

The sublingual gland is quite small, elongated, and lies
craniad of the submaxillary. Its duct extends parallel with
that of the submaxillary and opens within the mouth upon
the same papilla beneath the tongue. The molar gland is very
small and lies near the angle of the mouth ventrad of the pa-
rotid. Its several ducts, which are not easily demonstrated,
pass through the cheek to open within the mouth. The zygo-
matic or infraorbital gland lies on the lateral part of the orbit

Fig. 72. — Lateral Aspect of the
Head with the Skin Removed.
cr. Carotid artery; es, esophagus;
Im, lymphatic gland; nr, vagus and
sympathetic nerves; 5?w, submaxillary
gland; tr, trachea; v, cervical vertebra.

144 ELEMENTS OF MAMMALIAN ANATOMY

on the ventro-lateral surface of the eye-ball. It may be seen
by cutting away the zygomatic arch and the masseter muscle.
From near the ventral angle of the gland a duct leads to the
roof of the mouth posterior to the molar tooth.

The liver (hepar) is the largest gland in the body and is
situated immediately caudad of the diaphragm (Fig. 56), and
in contact with the right lateral and cranial surfaces of the
stomach. It is strongly convex on its cranial aspect while its
opposite surface presents a deep concavity occupied by the
stomach. Several deep incisions named fissures divide the
liver into five parts called lohes. The falciform or suspensory
ligament which is a fold of peritoneum joins the liver to the
diaphragm and extends into the large median fissure known as
the umbilical notch because during fetal life it shelters the vein
leading through the umbilical cord to receive nourishment from
the mother.

On the right side of the body from the umbilical notch is
the large right median lobe enfolding the gall bladder. On the
other side of the notch is a small left median lobe and a much
larger left lateral lobe. The right lateral lobe is dorsal of the
right median lobe, and is divided into two parts by a deep
cleft. A fifth lobe known as the Spigelian or caudate lobe is a
small triangular portion of the liver connected to the base of
the right lateral lobe and lying between the neck of the gall
bladder and the end of the stomach joining the esophagus.

The bile secreted by the liver passes through the several
ducts from the various lobes, to the main hepatic duct, which
may be seen by cutting away the liver from the right side of
the gall-cyst, and carefully picking off the peritoneum ensheath-
ing the vessels between the Spigelian lobe and the cystic duct.
The latter is somewhat convoluted in its course from the deeply
imbedded end of the cyst, to a point on the duodenum about
three centimeters from the pylorus. The main hepatic duct
joins the cystic duct (Fig. 66) near its middle. The common
duct thus formed is known as the common bile duct. When the

ORGANS OF DIGESTION 1 45

bile is secreted faster than it is permitted to enter the intestine,
it passes backward from the common bile duct into the cyst.

The bile aids in the absorption of the fats by the villi, and
renders the chyme alkaline. The formation of red blood-
corpuscles takes place in the liver of the embryo, while in the
adult, the liver destroys these corpuscles. The chief function
of this organ, however, is the formation of glycogen from the
sugars and starches eaten and the gradual transformation of
this glycogen into sugar as demanded for the nutrition of the
body. Diabetes mellitus is caused by a diseased liver or
pancreas which permits sugar to accumulate in the blood.

The pancreas (Fig. 66) is an elongated gland bent at a
right angle near its middle. The body of it lies dorsal to the
pyloric portion of the stomach, and the head lies close along
the concavity of the duodenum. It has two ducts, one of
which enters the duodenum in common with the common bile
duct, while the other enters about three centimeters further
caudad. The pancreatic juice acts on the starches, proteids,
and fats. A pancreatic bladder is sometimes found in the
cat, although it has not been described for any other vertebrate.
It probably has its origin as an accessory pancreas in which
the terminal lobe has become dilated to form the bladder while
the proximal portion atrophies, leaving only the duct (Boyden).
Another theory is that the pancreatic bladder is split off from
the gall bladder primordinum. "Neither of the two theories
as to the cause of pancreatic bladders will explain all known
cases. Both theories must therefore be retained " (Bremer '23) .

THE PERITONEUM

The peritoneum (Fig. 67) is the serous sac lining the abdom-
inal cavity and investing most of the organs therein contained.
The four portions of the peritoneum are known as the omenta,
the mesenteries, parietes, and ligaments.

The omenta are three in number, the largest of which is
the great or gastrocolic omentum, stretching caudad from the

146 ELEMENTS OF MAMMALIAN ANATOMY

dorsal abdominal wall and the greater curvature of the stomach,
so as to cover the intestine like an apron. It is composed of
four layers of peritoneum forming a closed sac, and bearing
more or less fat. Two layers form the ventral wall of the sac
attached to the stomach, and two layers are also present in
the dorsal wall of the sac which invests the pancreas.

The lesser omentum, or gasirohepatic omentum, extends cau-
dad from the liver to the pyloric part of the stomach and duo-
denum. Its two folds extend from the two sides of the portal
fissure, ensheathing the portal vein, hepatic artery, and cystic
duct. The gastrolienal ligament stretches from the cardiac
region of the stomach to the spleen, which it embraces, and
then proceeds to the diaphragm.

The mesenteries are the two layers of peritoneum suspend-
ing the intestine from the dorsal abdominal wall. There are
four mesenteries: the true mesentery, suspending the jejunum
and ileum; the mesoduodenum, suspending the duodenum; the
mesocolon, suspending the colon; and the mesorectum, sus-
pending the rectum.

The parietes or parietal peritoneum is that portion lining
the walls of the abdominal cavity. It is a closed sac in the
male, but in the female the uterine tubes open into it.

The ligaments are the layers of the peritoneum suspending
other organs than parts of the alimentary canal. The sus-
pensory or falciform ligament extends from the caudal surface
of the diaphragm and the abdominal wall, to the surface of
the liver, which its Hne of attachment divides into halves.
The round ligament is the thickened free caudal border of the
suspensory ligament. It is the remains of a vein which in
fetal Hfe joined the offspring to the mother. A third Kgament
connects the dorsal border of the liver with the diaphragm.
The broad ligaments of the uterus are the folds of peritoneum
which embrace the uterus, the uterine tubes, and the ovaries.
The ovarian ligaments are short cords extending from the ends of
the uterine cornua to the ovaries. The round hgaments of the

ORGANS OF DIGESTION I47

uterus pass from the sides of the uterus to the brim of the
pelvis.

The peritoneum is called a serous membrane because of the
colorless serum secreted by it. Other serous membranes are
the pericardium of the heart, the pleura lining the thoracic
cavity and investing the lungs, and the synovial membranes
of the joints. Serous membranes invest only such cavities as
are not exposed to the air. All other cavities are lined by
mucous membrane. A serous membrane consists of a layer
of fibrous connective tissue covered by plate-like endothelial cells.

REMARKS ON THE MAMMALIAN DIGESTIVE SYSTEM

The digestive system of mammals varies somewhat among
the different groups. In carnivorous animals, as a rule, the
alimentary canal is much shorter than in herbivorous. In
the wildcat the canal is four times the length of the body,
while the canal of the sheep is twenty times as long as the

Tdir

Fig. 73. — Diagram of the Stomach of a Ruminant.
a. Dotted line showing the direction of the food in the process of digestion;
abom, abomasum; du, duodenum; oe, esophagus; ps, psalterium; rt, reticulum.

body. In man it is about nine times as long as the distance
from the crown of the head to the coccyx. In Ruminants,
such as the cow and the sheep, the stomach is very large and
divided into four chambers — the rumen or paunch, reticulum,
psalterium or many plies, and ahomasum (Fig. 73). The rumen
and reticulum serve as mere storage cavities, from which
the food returns to the mouth for thorough mastication, and
then passes direct, by means of a groove in the esophagus, into
the psalterium, and finally on to the abomasum. The latter
is the true stomach, and is provided with gastric glands. In

148 ELEMENTS OF MAMMALIAN ANATOMY

the camels the rumen and reticulum have connected with
them pouch-like diverticula for the storage of water. The
constricted openings of the pouches into the rumen or reticu-
lum may be entirely closed by sphincter muscles.

In man and the higher apes there is present an attenuated
extension of the cecum known as the vermiform appendix. In
the fetus of man it is proportionally longer than in the adult.
In the herbivorous mammals, such as the cow and rabbit,
the cecum is greatly enlarged, so as to play an important
part in digestion. In a few forms, such as the sloths, some
Cetacea, and a few Carnivora, the cecum is absent.

The lowest mammals, the Monotremata, resemble birds and
reptiles in possessing a cloaca into which open the rectum
and the urinary and genital ducts. The cloaca opens externally
through the anus. Salivary and thyreoid glands, pancreas,
and the liver are present in all mammals, but the gall-cyst is
absent in Cetacea, the Perissodactyla, Hyracoidea, and a few
Rodentia. The liver is usually relatively larger in fat-eating
animals.

LABORATORY STUDIES AND SUGGESTIONS

1. Describe the fauces.

2. Describe in detail every feature visible on the dorsal surface of the tongue.

3. Give the number of fangs in each tooth of the permanent set.

4. Give the number of each kind of teeth in the two sets.

5. Draw two aspects of the sectorial tooth.

6. How thick is the enamel of the teeth?

7. Name some mammals which do not have enamel on the teeth.

8. Name some toothless mammals.

g. Name some mammals having only one set of teeth.
10. Give the dental formulae for three ungulates.
ir. In what animals are some of the teeth greatly enlarged?
12. Do any ruminants have upper incisors?
. 13. Name the important features of the pharynx.

14. Name every organ in the abdominal cavity, telling with what other
organs it is in contact.

15. Describe as much of the peritoneum as you can see in your specimen.

16. Draw the alimentary canal in its natural position, showing all ducts
leading into it, and label all parts.

ORGANS OF DIGESTION 1 49

17. How much longer is the small intestine than the large one?

1 8. On what does the length of the canal in different mammals largely depend?
ig. J\Iake a section of a portion of the wall of the stomach and draw what is

seen, labelling all parts.

20. Make a section of the small intestine, draw what can be seen by naked
eye or simple microscope.

21. About how many villi to each square millimeter?

22. Describe the two channels through which the food passes from the intes-
tines to the heart.

23. Make a somewhat diagrammatic drawing representing that part of the
venous system conveying the food from the intestines to the heart.

24. What is the size of the cecum in other mammals than the cat?

25. Give the location, size, and form of the salivary glands.

26. Name the lobes of the liver in order of their size.

27. How is the liver held in place?

28. Draw the pancreas, showing ducts leading to the intestine.

29. Draw the complex stomach characteristic of many ruminants.

30. What is the cloaca and in what mammals is it present?

THE VASCULAR SYSTEM

The vascular system is composed of the central forcing
muscular organ, the heart; a system of vessels, the arteries,
carrying the blood from the ventricles to the lungs and all
parts of the body; a system of vessels, the veins, returning
the blood to the atria; and numerous microscopic vessels, the
capillaries, connecting the termination of the arteries with
the origin of the veins.

THE HEART

The location of the heart in the cat may be seen by removing
the ventral thoracic wall, but for the study of the parts, the
heart of an ox or a sheep will be found more satisfactory. The
heart of the cat Kes between the lungs (Fig. 86) in the thoracic
cavity a little to the left of the median line. The caudal end
is the apex, and the cranial end is the base. The entire organ
is invested in a fibro-membranous sac the pericardium, which
when cut permits the pericardial fluid to run out. The walls of
this pericardial sac comprises two layers, the visceral layer or epi-
cardium, which closely invests the heart and a perietal layer, or
the pericardium proper, which forms a loose sac. All the
blood-vessels originate from the dorsocranial aspect of the heart.

It is composed of a right and left half, each of which con-
sists of an atrium or auricle and a ventricle. The separation
between the two halves is apparent on the ventral surface. The
atria receive the blood from the veins and pass it to the ven-
tricles, which disperse it through the arteries. There is no
aperture between the atria or the ventricles. The atrio-
ventricular opening between the right atrium and the right
ventricle is guarded by the tricuspid valve which prevents the
blood from returning into the atrium when the systole or con-
traction pushes the blood into the pulmonary artery. The

150

THE VASCULAR SYSTEM

151

left atrioventricular opening is guarded by the bicuspid or
mitral valve. These valves may be displayed by cutting away
the caudal half of the ventral wall of the ventricles, when the

Fig. 74. — Photograph of the Ven-
tral Aspect of the Human Heart
Injected.

a. Aorta; b, left ventricle; c, carotid
arteries; d, right ventricle; e, esophagus;
I, left atrium; n, right atrium; s, sub-
clavian artery; t, trachea; v, superior
vena cava. H natural size.

Fig. 75. — Heart Viewed Ven-
trally, with Ventral Half of
THE Atria and Ventricles Cut
Away and the Atria Drawn
Laterad. Partly diagrammatic.

a. Orifice of the aorta; ao, aorta;
aao, arch of the aorta; ap, orifice of
the precava; as, orifice of the post-
cava; Iv, left pulmonary veins; Ivn,
left ventricle; mi, mitral or bicuspid
valve; la, left atrium; -p, orifice of
the pulmonary veins; pc, inferior
vena cava; pre, superior vena cava;
ha, orifice of the pulmonary artery;
pYV, right pulmonary veins; rv, right
ventricle and one of the right pul-
monary veins; ra, right atrium; rp,
right pulmonary artery; Ir, tricuspid
valve; xp, left pulmonary artery.

chordcz tendinecE, delicate tendinous cords, will be seen extend-
ing from the margins of the translucent membranous valves
to the trabecuLT carnese or muscular projections on the walls

152

ELEMENTS OF MAMMALIAN ANATOMY

of the ventricles. The walls of the atria are thin in comparison
with the walls of the left ventricle, which are twice as thick
as the walls of the right ventricle (Fig. 76).

The walls of the heart are made up chiefly of a peculiar type of
striped muscle-cardiac muscle forming the myocardium. In

1.^

Fig. 76. — Ventral Aspect of the
Heart with Its Caudal Third Cut
OFF Transversely.

a. Adipose tissue; be, innominate
artery; la, left atrium; Iv, left ven-
tricle; Ic, left carotid artery; o,
ductus arteriosus; pv, pulmonary
vein; ha, pulmonary artery; pc, su-
perior vena cava; psc, inferior vena
cava; ra, right atrium; re, right
carotid artery; rs, right subclavian
artery; rv, right ventricle; sh, left
subclavian artery; Ir, trachea.

Fig. 77. — Dorsal Aspect of the
Heart of the Cat.
ao. Aorta; ap, apex; as, azygos
vein; he, innominate artery; ea,
coronary artery; cv, coronary vein; I,
left atrium; Ic, left carotid artery;
Ish, left subclavian artery; p, inferior
vena cava; pc, superior vena cava;
pa, pulmonary artery dividing into
its right and left branches; ra, right
atrium; re, right carotid; rs, right
subclavian; v, pulmonary veins.

addition to the cardiac muscle there are certain other fibers
known as Purkinji fibers which form a network just below the
endocardium. In 1893 W. His Jr. discovered a bundle of
muscle fibres arising in the posterior wall of the right atrium
which extends down into the ventricular septum and connects
the atrial and ventricular musculature. This has since been
known as the atrioventricular bundle of His. In 1906 Tawara

THE VASCULAR SYSTEM 1 53

demonstrated that the Purkinji fibers were parts of the bundle
of His and in 1908 Retzer proposed the name sinoventricular
system for the entire apparatus and suggested that it is neuro-
muscular in nature. Miss Lydia Dewitt in 1909 succeeded in
making a very complete reconstruction of the entire system in
man, dog, sheep, calf and cat. The system is of interest because
it seems to have to do with the coordination of atrial and ventri-
cular rhythm and because of its relations to certain pecu-
liar pathological conditions, such as Stokes-Adams disease.
Whether it may originate rhythmic impulses in the heart is
still a problem for investigation.

The atria are very small when not injected, and may by
the beginner be cut away with the pericardium and surround-
ing adipose tissue. The right atrium receives three veins, the
superior vena cava, inferior vena cava and coronary sinus, all
of which enter its dorsal aspect. The slit-like opening of
the coronary sinus is guarded by the semilunar valve of Thehesiiis^
valvula sinus coronarii (Thebesii). The portion of the atrium
into which the above veins open is the sinus venosus. At the
dorsal part of the septum which divides this atrium from the
adjoining one is an oval depression, the fossa ovalis, where,
in an embryo, the two atria communicated. The left atrium
is in contact with the right dorsally, and receives three pul-
monary veins (Fig. 77).

The right ventricle is smaller than the left. It makes a half
spiral turn about the left and terminates at its cranial end into
the pulmonary artery. The portion between the atrioventri-
cular opening and the pulmonary artery is known as the conus
arteriosus. Between it and the pulmonary artery are three
pocket-like semilunar valves which prevent the return of the
blood. Between each valve and the wall of the artery is a
pulmonary sinus, or sinus of valsalva. The left ventricle gives
origin to only one important vessel, the aorta, which arches
dorsally around the left atrium, and at the apex of the arch
gives off two branches, the innominate, and the left subclavian.

154 ELEMENTS OF MAMMALIAN ANATOMY

Three semilunar valves also guard the mouth of the aorta, each
of which partly conceals an aortic sinus, sinus aortae [Valsalva?].
The arteries of the heart may easily be distinguished from the
veins by the fact that the walls of the former are much thicker.

THE ARTERIES OF THE TRUNK

The blood-vessels form two systems of circulation; the one
known as the pulmonary circulation includes the arteries carry-
ing blood from the right ventricle to the lungs, and the veins
returning the blood from the lungs to the left atrium; the other,
known as the systemic circulation, includes the arteries con-
veying the blood from the left ventricle to all parts of the
body, and the veins returning the blood to the right atrium.

The pulmonary artery (A. pulmonalis) is united with the
aorta by a ligament, ligamentum arteriosum or ligamentum
Botalli, which represents the remnant of an embryonic connec-
tion between the two vessels, ductus Botalli (Fig. 88c). The
ligament is sometimes obliterated in the adult.

The main artery of the systemic circulation is the aorta,
which, beginning in the left ventricle, arches dorsal to the
heart and extends along the spinal column to the tail. That
portion in the thoracic cavity is termed the thoracic aorta,
while that portion in the abdominal cavity is the abdominal
aorta. Three semilunar valves guard the mouth of the aorta
at its opening from the ventricle, in order that the blood may
not be forced back into the heart by the contraction of the
muscular coat of the arteries.

The branches of the thoracic aorta are as follows: the right
and left coronary, arising from the aortic sinus are distributed
to the walls of the heart. From the arch of the aorta arise
two branches; first, the innominate (A. anonyma), giving rise
to a small mediastinal artery and the left and right carotids
supplying blood to the head and neck. The anonymous
artery then continues as the right subclavian to supply th^

THE VASCULAR SYSTEM

155

arm and hand. Second, the left
subclavian, which supplies the
left arm, brain, and sternum.

There may be considerable
variation in the order and arrange-
ment of these branches as may be
seen by consulting Figs. 78 and 84.
The innominate artery has some-
times been called the brachio-
cephalic. Ten pairs of intercostal
arteries supply the intercostal
spaces, muscles of the back, and
the spinal cord. Two bronchial
arteries go to the lung tissue.
Two to four esophageal arteries
are distributed to the esophagus.
Two or three pairs of lumbar
arteries pierce the muscles of the
back.

The abdominal aorta gives off
the following branches : the celiac
axis, the superior mesenteric, the
adrenolumbalis, a pair of renal, a
pair of genital, an inferior mesen-
teric, a pair of iliolumbar, seven
or eight pairs of lumbar, a pair
of external iliacs, a pair of internal
iliacs, (hypogastric), and a caudal
artery (Fig. 78).

The celiac axis is a large branch
arising just caudad to the dia-
phragm and gives off the hepatic
branch to the liver, pancreas,
and duodenum, the gastric (gas-
trica sinistra) to the stomach, and

Fig. 78. — Chief Arteries of the
Trunk, Ventral Aspect.
ar, Arch of the aorta; be, innomi-
nate; ce, celiac axis; cd, caudal; e, gas-
tric; /, gastric; gr, gastric; gas, gas-
troduodenalis; hp, hepatic; ht,
location of heart; icn, intercostals;
ic, external iliac; it, internal iliac;
il, iliolumbar; im, inferior mesenteric,
Is, left subclavian; //)/, left pulmonary;
m, splenic; o, splenic; r, right pul-
monary; re, renal; sp, splenic trunk;
Sfns, superior mesenteric; sm, sper-
matic or ovarian; s, adrenolumbalis;
1 1 2, 3, 4, 5, and 6, lumbar arteries.

156 ELEMENTS OF MAMMALIAN ANATOMY

is continued as the splenic, supplying the pancreas and the
spleen. The phrenic artery, supplying the diaphragn, some-
times arises from the celiac axis, but usually from the adrenolum-
balis.

One or two small branches (As ventriculi dorsales) may arise
from the celiac near its division, but frequently they are given
off by the left gastric artery.

The hepatic branch of the celiac axis gives off the gastro-
duodenalis just before entering the liver. Within the liver the
heptic breaks up into branches for the several lobes and a
cystic branch to the gall bladder. The gastroduodenalis
soon divides into three branches: the pyloric (A. pylorica) to
the pylorus and the lesser curvature of the stomach. Its
terminal branches anastomose with the left gastric, {h) The
pancreaticoduodenalis superior, to the duodenum and pancreas.
Its terminal branches anastomose with those of the pancreatico-
duodenalis inferior, (c) The gastroepiploica dextra, to the
greater curvature of the stomach and anastomosing with
the terminal branches of the splenic artery (A. lienalis). The
gastrica sinistra supplies the lesser curvature of the stomach
and anastomosis with the pyloric artery.

The superior mesenteric is about the same size as the celiac
axis, and arises w^ithin one centimeter caudad. It sends
branches to the pancreas and both intestines. The adreno-
Inmhalis is a small branch on the left dividing into the adrenal,
phrenic, and muscular. The superior mesenteric gives off
four large branches and breaks up into about sixteen smaller
ones, {a) Pancreaticoduodenalis inferior, to the pancreas and
duodenum, anastomosing with the gastroduodenalis superior.
{h) Colica media to the colon. It divides into two branches,
one anastomosing with the colica dextra and the other with the
inferior mesenteric, (c) Colica dextra, to the colon and anastom-
osing with the colica media and the ileocolica. {d) Ileocolica,
supplies the cecum and ileocecal valve and anastomoses with
the colica dextra and branches of the superior mesenteric. The

THE VASCULAR SYSTEM 157

sixteen or more smaller branches supply the small intestine.
The renal arteries supply the kidneys and sometimes the adrenal
bodies. Occasionally the spermatic artery may arise from the
renal and in rare instances the phrenic artery has a similar
origin. The genital arteries are small, and arise from one to
two centimeters caudad of the renal arteries. They pass
obliquely caudad to the ovaries in the female, and more directly
caudad to the testes in the male. The ovarian arteries are
larger than the spermatic. The inferior mesenteric is almost
as large as the superior mesenteric. It is distributed to the
large intestine. Its two large branches are, the colica sinistra,
and the superior hemorrhoidal. The iliolumbar arteries are
small branches supplying the muscles of the iliac region.
Four of live pairs of lumbar arteries are given off from the
dorsal side of the aorta at regular intervals between the dia-
phragm and the origin of the external ihac arteries. They
supply the muscles of the back and spinal cord. The external
iliac arteries are the largest branches of the abdominal aorta
and carry blood to the hind-limbs. The internal iliac arteries
arise more than a centimeter caudad to the external iliacs and
furnish blood to the pelvic viscera and the muscles of the
innominate region. The caudal (sacraHs media) artery is the
continuation of the aorta beyond the origin of the internal
iliacs. It extends into the tail (Figs. 78 and 84).

ARTERIES OF THE HEAD AND NECK

From the arch of the aorta arise the innominate and left
subclavian, which supply the sternum, neck, head, and anterior
extremities with blood. The innominate gives off the left
carotid and then divided into the right carotid and right sub-
clavian (Fig. 79). Sometimes the two carotids arise as a single
trunk from the innominate, which is then continued as the right
subclavian. In this case the common trunk of the carotid
usually bifurcates within one or two centimeters of its origin.

is8

ELEMENTS OF MAMMALIAN ANATOMY

forming the right common carotid and the left common carotid,
lying on the respective sides of the trachea beneath the sterno-
mastoid and the sternohyoid muscles. The vagus or tenth

Fig. 79. — Ventral Aspect of the Arteries of the Head and Neck.
The carotids with their branches have been drawn laterad.
a. Internal maxillary; ac, anterior cerebellar; ce, median cerebral; cr, posterior
cerebral; cp, posterior cerebellar; ex, carotid plexus, many of whose branches
reunite in one; ex', which is cut off; ex, external carotid; em, external maxillary;
ine, origin of internal carotid; inc', union of internal carotid with circle of Willis;
ia, inferior alveolar; iv, infraorbital; i, optic chiasma; li, lingual; mm, middle
meningeal; ms, muscular; oe, occipital; ol, anterior cerebral; pi, palatine; pa,
posterior auricular; s, anterior spinal; th, thyreoid; x, hypophysis; I, 2, 3, 4, 5,
and 6, transverse foramina in cervical vertebrae.

cranial nerve and the sympathetic trunk lie in the same sheath
with the carotid (Fig. 72).

THE VASCULAR SYSTEM 1 59

Each carotid artery in the neck region gives off the following
branches: an inferior thyreoid to the trachea and oesophagus, a
superior thyreoid to the thyreoid cartilage and gland, and a
muscular to the muscles of the neck. At the base of the skull,
about the middle of the bulla of the temporal bone, a slight
enlargement of the vessels is seen, from which arises the very
small internal carotid, leading through the foramen lacerum
medius to the base of the brain, where it joins the circle of Willis.
The continuation of the common carotid is now known as the
external carotid. This, after giving off a lingual branch to the
tongue, an external maxillary branch to the lower jaw, a post-
auricular branch, and a superficial temporal branch, turns to
pass along the medial aspect of the mandible, where it is named
the internal maxillary, whose main branches are the inferior
alveolar, the middle meningeal'^ supplying the dura mater, several
branches to form the carotid plexus, a palatine, sphenopalatine,
and infraorbital. The latter is the direct continuation of the
internal maxillary. It supplies the upper teeth, lower eyelid,
parts of the nose, and upper lip. An ophthalmic branch, sup-
plying structures in the orbit, may arise from the carotid
plexus or the internal maxillary. The branches of the external
maxillary artery are the submental to the symphysis of the
lower jaw, and the superior and inferior labial arteries.

The vertebral artery is the first branch given off by either
subclavian. It proceeds dorsad and craniad to the sixth cer-
vical vertebra, whence it extends through the transverse for-
amina of the cervical vertebrae (vertebrarterial canal) and
foramen magnum, to a junction with its fellow in the median
line on the ventral aspect of the medulla oblongata. The
union of the two vertebral arteries forms the basilar artery,
which, after giving off several branches to the medulla and
cerebellum, divides craniad of the pons Varolii, forming the
circle of Willis around the infundibulum and the optic chiasma
at the base of the brain. The circle of Willis receives the

* The middle meningeal may arise variously, frequently it arises from the
intracranial portion of the carotid plexus, Fig. 79 (Norris).

l6o ELEMENTS OF MAMMALIAN ANATOMY

internal carotid and gives off several arteries to the cerebrum.
In man the internal carotid is much larger proportionately
than in the cat (Fig. 74). The branches of the basilar artery-
are the posterior inferior eerebellar, anterior cerebellar and pos-
terior cerebral arteries.

THE ARTERIES OF THE THORACIC LIMB

There is more or less variation in the branching of the arteries
in the limbs. No two cats are found exactly alike as to their
arteries or veins. The same is true of all other mammals.

The subclavian artery, which on the right side springs from,
or is merely a continuation of, the innominate and on the left
side arises from the arch of the aorta, supplies the forelimbs
with blood (Figs. 79 and 80). When the subclavian reaches the
armpit, it is called the axillary artery, and its continuation
along the humerus is the brachial artery. A continuation of the
same artery along the radius is the radial artery, furnishing a
large part of the blood to the fingers.

Four branches arise from the subclavian: (i) the vertebral
artery, extending to the brain through the transverse foramina
of the cervical vertebrae (2) the internal mammary, arising
from the ventral side of the subclavian opposite the origin of
the vertebral, and extending along the visceral surface of the
sternum and sometimes supplying the pericardium of the
heart; (3) the costocervical axis, arising near the vertebral
artery, it gives off the superior intercostal artery supplying the
first and second intercostal spaces and some deep muscles of
the neck, and the transversa colli to the serratus anterior and
continues as the deep cervical (cervicales profunda) to supply
the deep muscles of the neck; and (4) the thyreoid axis, extend-
ing craniad giving off the ascending cervical to some muscles of
the neck, and the transverse scapular to the lateral aspect of
the scapula (Fig. 80).

The axillary artery gives origin to three branches: (i) the
anterior thoracic, supplying the pectoral muscles; (2) the long
thoracic, distributed chiefly to the latissimus dorsi; and (3) the

THE VASCULAR SYSTEM

i6t

subscapular, which is ahnost as
large as the continuation of the
axillary, now called the brachial
from this point on. The sub-
scapular, about a centimeter
from its origin gives off the
thoracodorsalis to the teres
major, latissimus dorsi, and epi-
trochlearis muscles; and the
posterior circumflex which winds
around the neck of the humerus
to its distribution in the triceps
and deltoid muscles. The sub-
scapular may also give origin to
the anterior circumflex and deep
branchial arteries, although
these usually arise from the
brachial.
The brachial artery, in addition
to several muscular branches,
gives origin to the anterior cir-
cumflex, superior profunda, the
nutrient, and anastomotica
magna. The anterior circum-
flex supplies the biceps and head
of the humerus. The superior
profunda is distributed to the
muscles on the caudal aspect of
the humerus. The nutrient
artery enters the nutrient fora-
men of the humerus. The an-
astomotica magna or superior
ulnar collateral artery is the
small branch supplying the con-
vexity of the elbow. The
superior collateral radial artery
rises at about the same point

Fig. 8o. — Arteries of the Forelimb;
Ventral Aspect.
a. Digital artery, aw, anastomotica
magna; ac, anterior circumflex; ai, an-
terior interosseous; ax, axillary; at,
anterior thoracic; b, digital artery;
be, innominate; br, brachial; c, dorsal
branch of the radial where it passes
between the second and third metacar-
pals to the palmar side; ex, circum-
flex; is, superior intercostal; Is, left
subclavian; //, long thoracic; m, branch
to extensor muscles; nt, nutrient; pi,
posterior interosseous; r, radial; rd,
radial recurrent; sf, supracondyloid
foramen of the humerus; spr, superior
profunda; sb, subscapularis; sp, supra-
scapularis; si, sternal; th, thyreoid
axis; id, ulnar; iir, ulnar recurrent;
vl, vertebral.

1 62 ELEMENTS OF MAMMALIAN ANATOMY

in company with the median vein of the elbow (v. medi-
ana ciibita). It passes to the ventroradial border of the
forearm and accompanies the cephalic vein and superficial
nerve to the wrist where it turns onto the dorsal side of
the hand, giving rise to the dorsal digital arteries of the
hand (Aa. digitales dorsales manus). The brachial artery-
after passing through the supracondyhoid foreman takes the
name of radial.

The radial artery, which lies deep beneath the flexor muscles
on the caudal aspect of the proximal half of the radius (Fig.
80), becomes superficial along its distal half, where the vessel
is covered by skin and fascia only. In the region of the wrist, it
curves dorsad and then pierces between the second and third
metacarpals to the palmar side, where it sends branches to each
of the digits, and forms the palmar arch by anastomosing with
the ulnar artery beneath the flexor muscles. In addition to a
few small branches, the radial gives off the following: the
radial recurrens, supplying the concavity of the elbow; the
ulnar recurrens, supplying the convexity of the elbow; the
posterior interosseous, passing caudad between the radius and
the ulna to the extensor muscles; the anterior interosseous,
passing along the cranial side of the interosseous membrane;
the ulnar, extending beneath the flexor muscles, which it sup-
plies, to the palm, where it anastomoses with the radial to form
the palmar arch; and the volar branch, supplying the super-
ficial palmar region. The ulnar and arterior interosseous
frequently arise from the same trunk, as shown in the figure.
The ulnar artery in the cat is so small that it is frequently not
filled by the starch injection, but in man it is larger than the
radial.

THE ARTERIES OF THE HIND-LIMB

As in the forelimb, the branching of the arteries in the hind-
limb varies considerably in different specimens. The main
artery of the leg lies on the ventral or medial aspect of the femur,

THE VASCULAR SYSTEM

163

passing obliquely to the caudal side of the knee-joint, where it
divides into two branches (Fig. 81), one extending along the
cranial, the other along the caudal aspect of the crus. The
cat, or at least the caudal half of a cat, should be fastened to the
dissecting tray on its back, the abdominal wall removed, and
the viscera pushed laterad to demonstrate the origin of the
artery of this limb. As in the forelimb, the main artery in
different portions of the leg takes the name of the corresponding
region.

Fig. 81. — Arteries of the Right Leg. Ventral Aspect.
a. Aorta; at, anterior tibial; af, anterior femoral; cd, caudal; eg, epigastric;
em, external malleolar; fem, femoral; itn, internal malleolar; il, external iliac;
it, internal iliac; hi, iliolumbar; m, digital; n, digital; o, digital; p, peroneal;
pa, profunda; pf, posterior superior femoral; pi, posterior inferior femoral; pn,
plantar; pp, popliteal; pt, posterior tibial; ps, saphenous.

The external iliac is the largest artery arising from the aorta
in the lumbar region. It gives off but one important branch,
the deep artery of the thigh (A. profunda femoris), which,
extending caudad soon gives off three branches a large inferior
epigastric artery to the abdominal wall, a branch to the

164 ELEMENTS OF MAMMALIAN ANATOMY

bladder then a smaller branch to the external genital organs,
and numerous branches to the muscles on the caudal aspect of
the femur. The branches of the hypogastric (internal iliac) are
the umbilical to th(ih\'dddcT , the superior gluteal to ihepdvicwsiW,
the middle hemorrhoidal to the rectum and the inferior gluteal.

The femoral artery, which is a continuation of the external
iliac, extends along the medial aspect of the femur. In the
proximal half of its course it is quite superficial, and lies in a
triangular space known as Scarpa's triangle and in Hunter's
canal, but the distal portion is covered by the gracilis, sar-
torius, and semimembranosus muscles. It furnishes four
important branches: the circumflexa femoris lateralis supplying
mainly the quadriceps extensor muscle; the muscular branches
supplying the adductor and hamstring muscles; genu supre?na
to the knee, the saphenous, accompanying the saphenous nerve
and vein to the foot, where it branches and anastomoses with
the plantar artery ; and the .sural artery supplying mainly the
gastrocnemius group of muscles (Fig. 49) .

The popliteal artery is the continuation of the femoral artery
in the popliteal region on the caudal aspect of the knee-joint.
One or two articular branches are given off here to the joint, in
addition to the posterior tibial, which supplies the deep muscles
of the crus.

The anterior tibial artery is the continuation of the popliteal
on the lateral cranial aspect of the tibia, adjacent to the bone.
By separating the tibialis anticus and extensor longus digitorum
muscles, this artery is well displayed. Near the knee-joint a
small branch, the peroneal, is given off, and passes to the dorsal
aspect of the foot, where it anastomoses with the dorsal branch
of the saphenous, forming a superficial arch sending branches to
the digits. The peroneal is so small that it is frequently not
injected. In the tarsal region two branches, an external or
lateral anterior malleolar and an internal or medial anterior
malleolar, are given oii. A centimeter or two distal to the latter
branch, the main artery passes between the second and third

THE VASCULAR SYSTEM 1 65

metatarsals to the deep plantar region, where it receives
an anastomosing branch from the saphenous forming the
plantar arch, and sends off branches to the digits. {Aa digitales
plantares.)

THE VENOUS SYSTEM

The veins are the vessels returning the blood to the heart.
As a rule, veins carry only impure blood, but the pulmonary
veins returning blood from the lungs to the left atrium carry
pure blood. After death the veins can readily be distinguished
from the arteries by the fact that they have much thinner walls
than the arteries and are usually full of blood, while the arteries
are empty (Fig. 82). This is due to the fact that the thick
muscular coat of the arteries, by its contraction tends to drive
the blood into the veins, whose muscular coat is very thin.
The three coats composing the walls of the veins are the epi-
thelial, or tunica intima; the middle or muscular; and the tunica
adventitia, or outer elastic coat of fibro-areolar tissue. The
veins of the central nervous system and its membranes have no
muscular coat. While the only valves in the arteries are found
at their origin from the heart, the veins of the limbs, neck, and
the head possess numerous valves. These valves are formed by
semilunar folds of the epithelial coat, strengthened by fibrous
tissue (Fig. 83).

The main deep veins of the limbs accompany the arteries and
take the same names as the arteries. A superficial set of veins
is present also in the limbs. The large superficial vein on the
lateral aspect of the forelimb is the cephalic. The superficial
vein extending along the medial aspect of the hind-limb is the
saphenous.

The Veins of the Trunk, Head, and Neck. — There are
two chief venous trunks: the precava, or superior vena cava, and
the postcava, or inferior vena cava. Both vessels open into the
dorsal aspect of the right auricle or atrium. The veins received
by the inferior vena cava are thirteen in number. The phrenic

166

ELEMENTS OF MAMMALIAN ANATOMY

veins collect the l^lood from the diaphragm and empty into the
vena cava immediaUly caudad of the diaphragm. The several
hcpalic veins collect the blood from the liver, which must be
partly dissected away to see their entrance into the vena cava.

a b c d

Intima

Endothelium.
Inner elastic
membrane.

f Muscle fibers.

Media '

Externa

Conn, tissue. — ;

Outer elastic
membrane.

Conn, tissue.

Vasa
vasorum.

Fat cells. —

This portion is
shown enlarged
on the left.

Fig. 82. — A Section through a Hum.\n Ulnar Artery and Vein, Show-
ing THE Wall of the Artery on the Left and of the Vein on the Right.
The Upper Part of the Figure {a-d) is from a Section of the Same Ves-
sels Stained with Resorcin-fuchsin, an Elastic Tissue Stain. x 550.

a. Circular, and h, radial elastic fibers of the media of the artery; c, external
elastic membrane; d, elastic fibers in the media of the vein; e, circular, and g, longi
tudinal muscle fibers of the media; /, endothelium. {Lewis and Stohr.)

The two adrenohimhar veins return the blood from the supra-
renal bodies and body walls, lumbar veins to muscles of dorsal
wall and two renal veins carry the blood from the kidneys. The
left ovarian or spermatic vein is a tributary to the left renal, but

THE VASCULAR SYSTEM 1 67

the rigJit ovarian empties directly into the vena cava. A pair of
small iliolumbar veins collecting blood from the lumbar muscles
empty into the vena cava a centimeter or more craniad to the
large common iliacs. The union of the common iliac veins col-
lecting the blood from the hind-limbs and the pelvic region, and
the caudal vein, forms the beginning of the inferior vena cava.
The common iliac is formed by the union of the external and in-
ternal iliac veins in the pelvis. The former
is much the larger of the two.

The portal system begins with the veins
collecting the blood from the intestines,
pancreas, spleen, and stomach, and termi-
nates where the hepatic veins enter the vena
cava. The inferior mesenteric vein collects
the blood from the large intestine ; the superior T^

mesenteric, from the small intestines; the gas- pj^, g _y ^ j ^
trosplenic, from the spleen, stomach, and ^^^ Open. Arrow

Shows the Direc-

panereas; the coronary, from the lesser cur- tion of the Blood.
vature of the stomach; the gastro-epiploica, .^ "f fe^ edge "* if Thi
from the greater curvature of the stomach; valve,
and the pancreatoduodenalis , from the pan-
creas and duodenum. The last three may empty directly
into the portal vein or into one of the three branches first
named. Within the liver the blood is carried to the hepatic
lobules through the interlohiilar branches of the portal vein, from
which it is distributed to the intralobular sinusoids. It is
then collected by the central vein of the lobule and conveyed
through the hepatic veins to the postcava through which it reaches
the heart.

The superior vena cava (precava) extends from the union of the
innominate veins to the right atrium. Three important
veins empty into the superior vena cava: the azygos, collecting
blood from the intercostal spaces; the sternal, lying on the vis-
ceral surface of the sternum; and the right vertebral, which,
with its fellow, collects the blood from the deep muscles and

1 68 ELEMENTS OF MAMMALIAN ANATOMY

spinal cord in the region of the atlas, and after making a strong
anastomosis with the internal jugular vein, descends in com-
pany with the vertebral artery through the transverse foramina
canal of the first, six cervical vertebrae. The left vertebral vein
is a tributary of the left innominate (Fig. 84).

The imiominate vein is formed by the union of the subclavian
and the external jugular. Sometimes the vertebral vein joins
also in the union instead of emptying into the superior vena cava.
The subclavian vein returns the blood from the arm and accom-
panies the subclavian artery. The external jugular veins are
large vessels lying on either side of the neck beneath the platys-
ma myoids muscle. When the skin is removed, the veins are
plainly seen through this very thin muscle. The external jugu-
lar is formed ventral to the angle of the mandible by the union
of the anterior and posterior facial veins. The anterior facial
are united by a large transverse vein. The two tributaries of
the external jugular are the transverse scapular vein and the
internal jugular. The former receives the cephalic vein, a
superficial vein on the lateral aspect of the arm, and the latter
is the small vein returning from the brain.

A system of tube-like spaces, called sinuses, whose walls are
formed by the dura mater lined with epithelium, takes the
place of the large venous trunks within the cranial cavity.
These sinuses are usually not filled by a starch injection, but
may be filled by a gelatin mass. They cannot be dissected by
the beginner. The superior longitudinal sinus extends in the
median line beneath the roof of the skull, from the ethmoid
region to the tentorium cerebelli, where it bifurcates to form the
lateral sinuses, which proceed laterad and ventrad in the sub-
stance of the tentorium. The lateral sinus emerges from the
tentorium just caudad to the petrosal bone, where it follows
the groove to the jugular foramen. This groove may be seen
in a bisected or unroofed skull.

The superior petrosal sinus lies in the angle formed by the
junction of the tentorium and the petrosal bone, and unites

THE VASCULAR SYSTEM

169

Fig. 84. — Chief Arteries and Veins of the Cat.
Ad. lum., adrenolumbar; Anl. au., anterior auricular; Ant. Fac, anterior facial; Ant. ?nes.,
anterior mesenteric; Art. G. Sup., articularis genu suprema (vein); Articul. genu.' sup.,
articularis genu suprema (artery); Ax, axillary artery and vein; Brack., brachial vein;
Circum. fern, lat., circumflexa femoris lateralis (artery); Col. Rad. Sup., collateralis radialis
superior artery; Col. ul., collateralis ulnaris artery; Epigasl. inf., epigastrica inferior; Ex.
iliac, external iliac artery; Ex. Jug., external jugular vein; Hypog. V., hypogastric vein; Int.
iliac, internal iliac; Int. Jug., internal jugular; Int. mam., internal mammary; Inf. mes.,
inferior mesenteric; Inf. Thy., inferior thyreoid; Long. Tlior., long thoracic; Pos. Fac,
posterior facial; Ren., renal; SubcL, subclavian; Subment., submentalis vein; Subscap.,
subscapular vein; Trans., transverse vein; Trans. Scap., transverse scapular vein; Thor.-dors.,
thoracodorsalis artery; Vert., vertebral vein.

lyo

ELEMENTS OF MAMMALIAN ANATOMY

with the lateral sinus just before it reaches the jugular foramen.
The inferior petrosal sinus, collecting blood from the base of the
brain, lies in the groove ventral to the petrosal bone, and unites
with the lateral sinus at the jugular foramen. The union of
these sinuses at this foramen forms the internal jugular vein.

spmJ,

r.c

r.r

Fig. 85. — A, Ventral View of Heart and Main Arteries in the Trunk of
THE Rabbit. B, Arteries of Man.
a, Right atrium; ca, left carotid; c, ax, celiac axis; i. w, innominate; //, common
iliac; i. m. inferior mesenteric; /, r, left renal; r, r, right renal; r. c, right inter-
costals; sm, superior mesenteric; sp^n, spermatic; sa, sacral; sb, left subclavian.

which extends deep beneath the muscles of the neck with the
carotid artery. It joins the external jugular opposite the
shoulder-joint. At the base of the skull the internal jugular
gives off a large transverse anastomosing vein to the vertebral,

THE VASCULAR SYSTEM 171

SO that the blood from the vein may return partly by the latter
vessel.

The pulmonary veins convey the pure blood from the lungs
to the left atrium. There are three main trunks from each
lung. These six veins are arranged in pairs (Fig. 77), constitut-
ing a left pair from the left lung; a median pair, composed
of one branch from the right and one from the left lung; and
a right pair from the right lung. Each pair forms a common
trunk before entering the atrium. In order to demonstrate
these veins one must remove the heart and lungs from an in-
jected cat, and carefully dissect away the fatty and connective
tissues enveloping the vessels.

The peripheral connection between the arteries and veins
is by means of capillaries, which are microscopic vessels with
an extremely thin wall composed of a single layer of epithelial
cells. These capillaries are so abundant everywhere in the
flesh that a needle cannot be inserted without penetrating
some. They form a kind of mesh or network, so that every
cell may be supplied w^ith oxygen and food and discharge its
waste matter. All the blood carried to any portion of the
body by the arteries is not returned by the veins, as a consider-
able amount of the plasma and some of the white corpuscles
escape through the thin capillary walls and are returned to the
circulation by a system of vessels called lymphatics (Fig. 91).

DEVELOPMENT OF THE VASCULAR SYSTEM

In the cat as in all other vertebrates the vascular system
has its origin in the mesenchyme. Small spaces or clefts appear
among the mesenchymal cells, enlarge and fuse together to form
a network or plexus of channels. Following certain laws of
hydrodynamics the blood stream comes to flow along the most
direct line of least resistance. The channels thus formed are
usually oriented with respect to the longitudinal axis of the
body. Those carrying blood toward the central organ of
circulation develop into the venous system, while those carrying
the blood stream peripherally form the arterial system.

172 ELEMENTS OF MAMMALIAN ANATOMY

DEVELOPMENT OF THE HEART

The development of the heart in the eat has been carefully
worked out for the earher stages by Schulte ('16) and in the

Fig. 86a. — Cat Embryo ok Nine Somites. (Modified after Schulte, Am. Jour.

Anal., Vol. 20, p. 51.)
a, lateral hearts; b, digestive tract; c, nervous system.

Fig. 86&. — Cat Embryo of Twelve Somites. {Modified after Schulte.)
a, lateral hearts about to fuse; h, endothelial layer; c, myocardium.

pig by Miss Sabin ('17). According to Schulte the heart
develops by an approximation, fusing and looping of certain
lateral primordia lying in the dorsal wall of the open intestine

THE VASCULAR SYSTEM

173

in a cat embryo of about nine pairs of mesodermic somites
(Fig. S6a) . These ''lateral hearts " are the continuation forward
of the omphalomesenteric veins after they have reached the
intraembryonic region. Widely divergent at their caudal ends
they converge cranially so as to lie close together for a short
distance. The primordia consists essentially of two parts, an
inner endothelial layer which eventually becomes the endocardial
lining of the adult heart, and a heavier outer part, the myo-
epicardial mantle, which forms the muscular walls of the adult
organ. In an embryo of about twelve pairs of somites (Fig.
86^) the two lateral moities fuse in the midline of the body to

Aorta
Jruncus Anteriosus

Fretum Halleri

Ventriculus
Bui bus Cordis
rium

Fig. 86c.— Pig Embryo of Twenty Somites. (After Sabbi, Contrihiilions to
Embryology, Carnegie Institution of Washington, 226, plate 5.)

form a simple tube-like heart resembling in many respects
the condition found in the earlier fishes. The primitive heart
in its further development then bends on itself and twists
so as to bring the caudal or venous end forward and dorsal to
the cranial or arterial end. This is well shown in Fig. 86c
after Miss Sabin's figure of a pig embryo of about twenty somites.
Eventually by a fusion of parts and certain other changes the

174 ELEMENTS OF MAMMALIAN ANATOMY

venous portion is transformed into the atrial or auricular portion
of the adult heart and the arterial into the ventricular portion.
It is interesting to note that the heart in its embryonic develop-
ment passes through a stage in which there is a single circulation,
resembling the condition found in lower gill-breathing aquatic
vertebrates where only impure blood is found in the heart.
Also that an arterial arrangement is set up as though for a gill-
breathing animal. It is only later when the true lungs are
developed that the heart becomes four chambered and a double
circulation characteristic of higher vertebrates is established.
In connection with this change in the structure of the heart
there are certain transformations in the arrangement of the
arterial system changing it from the gill-breathing type to that
of the lung-breathing, a change that will be better understood
when compared with the phylogeny of the aortic arches shown
in Fig. 83.

DEVELOPMENT OF THE AORTIC ARCHES

The aortae and aortic arches are developed from an arterial
plexus in the region cranial and dorsal to the developing heart.
The aortge are developed from a plexus in the area vasculosa
along the lateral edge of the myotomes. This capillary plexus
appears to be developed in situ by the fusion of intercellular
mesenchymal spaces or clefts. According to Coulter ('09)
only the first aortic arch is complete in a cat embryo of 3 mm.,
although there are indications of the second and third arches
(Fig. 87a). These are completed at the time an embryo has
reached the length of 4.5 mm. and the fourth arch has begun
to be formed (Fig. 876). In a 5 mm. embryo the first arch
begins to degenerate, while the fourth is completed and the
sixth is begun (Fig. 87c). It is doubtful whether the fifth
arch is ever completed in the cat although rudiments of it
can be seen at a stage slightly older than five millimeters (Fig.
Sjd). Before the six millimeter stage is reached the sixth arch
is usually completed and gives origin to the pulmonary arteries

THE VASCULAR SYSTEM

175

Arch I

Pulmonary
Arteries

Vertebral.
Subclav^an-

FiG. 87. — Diagrams of Reconstructions of Aortic Arches in Cat Embryos.

{After Coulter, Anatom. Record, Vol. 3, p. 580.)

A. aortic arches of a Cat embryo of 4.5 mm. B. aortic arches of a Cat

embryo of 5 mm. C. aortic arches of a Cat embryo of 5 mm. D. aortic

arches of a Cat embryo of 5 mm. E. aortic arches of a Cat embryo of 10 mm.

176

ELEMENTS OF MAMMALIAN ANATOMY

(Fig. Syr). It is interesting to compare the embryonic history
of the aortic arches with the arrangement found in different

Fig. 88. — Modifications of the Aortic Arches in Different Vertebrates.
{From Kingsley's Comparative Anatomy of Veretebrates, after Boas.)
A. Primitive scheme; B. Dipnoian; C. Urodele; D. Frog; E. Snake; F.
Lizard; G. Bird; H. Mammal: c, celiac artery; da, dorsal aorta; db. Ductus
Botallii; ec, ic, external and internal carotids; p, pulmonary artery; s, subclavian;
va, ventral aorta. Vessels carrying venous blood back; those with mixed blood
shaded; those which disappear, dotted outlines.

vertebrates. The schematic diagrams in figure 88 A-H shows
the arrangement in fishes (A, B), amphibians (C, D), reptiles
(E, F), birds (G) and mammals (H).

THE VASCULAR SYSTEM 1 77

DEVELOPMENT OF THE VENOUS SYSTEM

The primary veins of the mammalian embryo are four pairs
to which there is early added a fifth pair. These are the pre-
cardinals, the postcardinals, the subcardinals, the umbilicals,
and later the supracardinals. These primary vessels may be
regarded as forming the fundamental ground plan common to
all vertebrates. The precardinals and postcardinals join
in the heart region to form a duct of Cuvier on each side which
open into the sinus venosus. The ducts of Cuvier also receive
the umbilicals. The subcardinals open into the postcardinals
some distance caudad of the duct of Cuvier. The subcardinals
and supracardinals play an important role in the formation of
the postcava. From these five pairs of veins are developed
the larger venous trunks of the adult.

A short outline of the history of the development of the post-
cava will serve to illustrate the complexity of vascular ontogeny
and of the interesting transformations taking place during the
embryological development of an animal. The account is
based upon the work done by Huntington and McClure on
the development of the postcava in the cat.

After the four primary systems have been differentiated from
the general plexus system the first important step is the forma-
tion of an anastomosis between the subcardinals in the neighbor-
hood of the origin of the omphalomesenteric artery from the
aorta, the intersubcardinal anastomosis. (Fig. 89, B.) At
about the same level and time there is also formed on each side
a subcardino-postcardinal anastomosis. During this stage of
development there is a rearrangement of the channels and
sinusoids of the liver so as to furnish a more direct route for
the blood stream through this organ to the heart so that most
of the blood from the posterior regions of the body passes
through the liver rather than through the duct of Cuvier.
There is thus established in the liver a broad channel which is
later to form the hepatic segment of the postcava. However,
in order to accomplish this there has been formed in the caval

178

ELEMENTS OF MAMMALIAN ANATOMY

Fig. 89. — Diagrams Showing the Development of the Postcava in the
Cat. (From Hytnan's Laboratory Manual of Vertebrate Anatomy, after Htinling-
ton and McClure.)

Crosshatching, cardinal system of veins and their derivatives; close stippling,
subcardinal system of veins and their derivatives; cross, vertical, and oblique
hatching combined, hepatic veins; open stippling, supracardinal system of veins
and their derivatives; vertical hatching, the renal collar.

Figs. A-G inclusive, showing various stages of development of the veins in
the cat. a, precardinal; b, postcardinal; (thoracic division) ; c, postcardinal (lum-

THE VASCULAR SYSTEM 1 79

mesentery a hepatico-subcardinal anastomosis (P'ig. 89B).
The result of this diversion of the blood stream through the
liver results in the dwindling of the postcardinals craniad of
this point. The growth of the pelvic regions of the embryo
due to the developing limbs is accompanied by an increase
in the size of the posterior part of the postcardinals (Fig. 89C).
There now appears a new pair of vessels in the prevertebral
regions, the supracardinal veins, which are destined to play a
very important part in the formation of the postcava. They
make connections with the postcardinals in the caudal regions
and also cranially (Fig. 89D). In the pig according to Sabin,
the supracardinal are more directly related to the duct of
Ciivier than to the postcardinals in that region. An anasto-
mosis is also made with the subcardinals at about the level of
the intersub cardinal anastomosis, the subcardino-supracardinal
anastomosis. In the same region there is also an intersupra-
cardinal anastomosis. The aorta is thus entirely surrounded
by a venous ring, known as the renal collar. The renal collar,
therefore, ''is formxcd by the pars subcardinalis of the postcava,
the intersubcardinal anastomosis, the right and left subcardino-
postcardinal anastomoses, the right and left supracardinals,
and the anastomoses between the supracardinals dorsal to the
aorta at this point, at which level the renal veins enter the col-
lar." (Fig. 89E.) Further development results in the complete
degeneration of the anterior segment of the postcardinal except
such part as may enter into the formation of the azygos and
such other changes as may be seen by consulting the diagrams
in figure 89.

''The embryonic veins which typically enter into the for-
mation of the adult postcava are the right supracardinal

bar division); d, duct of Cuvier; e, pars hepatica of postcava (hepatic communis
and ductus venosus Arantii);/, subcardinal; g, gonad; h, pars subcardinalis
of postcava (intersubcardinal anastomosis); i, supracardinal; 7, kidney; ;^,
renal collar (subcardino-supracardinal anastomosis); /, adrenal gland; m, vein to
adrenal; n, precava; o coronary sinus; p, left innominate; q, internal jugular; r.
subclavian; s, external jugular; t, external iliac; u, internal iliac.

I So

ELEMENTS OF MAMMALIAN ANATOMY

Fig. 90. — Composite Diagram of the Embryonic Veins of the Cat. {After
Huntington and McClure, Anat. Record, Vol. xx.)
L. Innom. V., left innominate vein; D. C, duct of Cuvier; Ao., aorta; P. Hep.,
pars hepatica; P. siibc, pars subcardinalis of postcava; I.S.A., intersubcardinal
anastomosis; Subc. supra., subcardino-supracardinal anastomosis; Subc. pc. an.,
subcardino-postcardinal anastomosis; R.V., renal vein; A., right postcardinal;
B., right supracardinal; C, left supracardinal; £>., left postcardinal; Uiol., iliolum-
bar; Ex. il. v., external iliac vein; /. il. v. internal iliac vein.

THE VASCULAR SYSTEM l8l

(Fig. 90), the right subcardino-supracardinal anastomosis
(subc. -supra, anas.) , the right subcardino-postcardinal anastomo-
sis (subc.-pc.-an.) the intersub-cardinal anastomosis (I. S. A.),
the pars subcardinalis (P. Sub) and the pars hepatica (P. Hep.)-"
Figure 90 is also introduced to aid the student interpret some
of the variations in the venous system likely to be found in
the cat. Huntington and McClure list some seventeen types
of variation which may be explained. (Anatomical Record,
Vol. 20, page 14.) There may be double postcava, persistence of
right postcardinal, or subcardinal, or in some animals and
in man of the renal collar. Students are advised to look for
and make records of such variations as they may find in their
dissection. They will find great pleasure in trying to interpret
them embryologically.

LABORATORY STUDIES AND SUGGESTIONS

1. What holds the heart in place?

2. Draw the ventral aspect of the heart with the pericardium removed and
label all features.

3. When the heart is detached from the body, how do you distinguish the
dorsal from the ventral aspect?

4. How many veins open into each atrium?

5. What arteries lead from each ventricle?

6. After dissecting write a detailed description of the valves of the heart.

7. Describe the difference in the appearance of the walls of the aorta and
vena cava.

8. From your dissection write a description of the features seen in each cavity
of the heart.

9. Name the branches of the thoracic aorta in order.

10. Name the branches of the abdominal aorta and tell what organs each
supplies.

11. Draw the celiac axis and its branches throughout their course and label
all parts.

12. Show by a drawing the relations of the aorta and venae cavae throughout.

13. Make a diagrammatic cross-section of the neck, showing location of
arteries and veins.

14. Describe the three routes by which blood may reach the brain and the
two routes by which it may be returned to the heart.

15. Name the arteries arising from the arch of the aorta,

16. Draw the inner or medial aspect of your dissection of the arteries of the
thoracic limb and label all parts.

1 82 ELEMENTS OF MAMMALIAN ANATOMY

17. Draw cross-section of arm at middle of humerus to show location of main
artery and vein.

18. Draw cross-section of the middle region of the forearm to show location
of chief arteries.

19. Draw outline of the bones of the manus and show relation of arteries to
the bones as seen from palmar aspect.

20. Draw outline of femur and show course of main artery in relation to the
bone as seen from medial aspect.

21. Draw outline of bones of the pes and show relations of the arteries to the
bones as seen from the plantar aspect.

22. At what points in its course is the chief artery of the pelvic limb most
superficial?

23. Describe the difference in structure of a vein and an artery.

24. What veins open into each atrium of the heart?

25. Name the veins returning the blood from each organ of the abdominal
cavity.

26. Draw the portal system and label all vessels.

27. Describe the veins returning the blood from the head.

28. Describe the chief blood sinuses in the skull.

29. Where are the valves found in the blood-vessels?

30. If the brachial vein were cut, how could the blood from the manus reach
the heart?

THE LYMPHATIC SYSTEM

The lymphatics constitute that part of the vascular system
which collects the colorless fluid called lymph from the tissues,
and the chyle from the small intestine, and conveys them to
the external jugular veins. The portions of the lymphatic sys-
tem originating in the villi of the small intestine and convey-
ing the chyle to the left thoracic duct are known as the lacteals
(Fig. 71, h).

The lymphatic system consists of four parts: (i) the lym-
phatic spaces between the skin and muscles in all parts of the
body, the spaces between the muscles adjacent to the bones,
and internal spaces such as those enclosed by the peritoneum
and pleura; (2) minute thin-walled vessels draining the spaces
just described and leading to larger vessels which empty into
the tracheal trunks or thoracic duct; (3) the glands, which
vary in size from a mustard-seed to two centimeters in diam-

THE VASCULAR SYSTEM 1 83

eter, and are located chiefly on the side of the neck, in the
axillary region, at the bifurcation of the trachea; in the inguinal
region, lumbar region, and mesentery; (4) the two tracheal
trunks and thoracic duct (Fig. 91).

One of the largest of the lymphatic spaces is the greater
cavity of the peritoneum. The cavity or the lesser peritoneum,
a large lymphatic space, may be shown by separating the layers
of the great omentum carefully. The cavity of the pleura
within the chest is also a large lymphatic space. Numerous
small lymph spaces are present in all parts of the body. The
beginnings of lymphatic capillaries draining these spaces are
invisible to the naked eye, but their union into larger vessels
may be demonstrated satisfactorily in a cat just killed, by
pulling forward the tongue, and injecting very slowly beneath
the skin, on its ventral aspect five or ten centimeters of a two
per cent, solution of Berlin blue in warm water. A very good
demonstration of the thoracic duct may be had by feeding the
cat a half pint of milk about two hours before killing, or by using
Gage's method described on page 13.

The lymph glands (Fig. 91) of the cat are not nearly so
numerous as in man. The largest lymph glands is the mesen-
teric lymph gland in the mesentery. It is considerably flat-
tened and about two centimeters long. It is formed by the
grouping of several smaller glands and was formerly known as
the pancreas Aselli. A few other very small lymphatic glands
are also present in the mesentery. The two largest lymph
glands of^ the head are just beneath the skin craniad of
the submaxillary gland. On the side of the neck beneath the
cephalohumeral muscle are three large lymph glands at the
cranial border of the scapula. A small axillary gland lies on
the caudal side of the axillary vein beneath the scapula. A
single popliteal gland is in the popliteal space, an inguinal gland
lies on each side of the penis, two or three iliac glands are near
the origin of the femoral artery, and a few small lumbar glands
lie in the lumbar region of the abdominal cavity.

184 ELEMENTS OF MAMMALIAN ANATOMY

All parts of the body have communication with the lym-
phatic vessels, which for the most part are so small as to be
invisible unless injected, when they are easily recognized by
their beaded appearance caused by the numerous valves within
them. There are two systems of vessels in the head and
extremities — the superficial and the deep. The former accom-
pany mainly the superficial veins, and the latter follow the
deep veins. On the outer aspect of the thoracic limb just
beneath the skin two vessels are present, which flow into the
cervical glands. They carry the lymph from the ball of the
foot and the skin of the foot and forearm. One or two deep
lymph-vessels are found accompanying the brachial vein and
artery, which convey the lymph from the bones and muscles
of the arm to the axillary gland.

In the pelvic limb two or three superficial vessels are pres-
ent transmitting the lymph from the foot of the popliteal
gland, whence two vessels proceed to the deep lymphatic sys-
tem. The lymph from the bones and muscles of the leg
reaches the iliac glands through two or three deep vessels lying
near the femoral vein and artery. The inguinal glands receive
most of the lymph from the skin of the leg.

The lymph from the superficial parts of the head flows
largely into the submaxillary lymph glands, while that from
the brain, tongue, esophagus, and larynx empties into the
laryngeal glands.

The lymph of the right forelimb, right side of the neck and
head, and right side of the thoracic wall is received by the
right tracheal trunk. The left tracheal trunk receives the
lymph from the left side of the head, neck and thoracic wall,
and the left forelimb. The thoracic duct receives the lymph
from the lungs, heart, all the abdominal viscera, and muscles,
and the hind-limbs. With but few exceptions, all the main-
lymphatic vessels pass through lymphatic glands before reach-
ing one of the three main trunks. In fact, the vessels bring-
ing the lymph to the glands may be said to terminate there.

THE VASCULAR SYSTEM

i8'

They are called afferent lymphatics. The lymph moves free
through the tissue of the gland, and on the opposite side is
taken up by the efferent lymphatics.

The right and left tracheal trunks
lie on their respective sides of the
trachea and empty into the ex-
ternal jugular vein in the common
jugular and jugulo-subclavian dis-
tricts together with the right
lymphatic and thoracic ducts.
The openings are guarded by
valves which prevent the blood
from entering the lymphatic trunk.

The thoracic duct (Fig. 91) is
the largest vessel of the lym-
phatic system, but is usually
invisible unless injected. It
extends from the region of the
kidneys on the dorsal aspect of
the body cavity, along the left
side of the spinal column, to

Fig. 91. — Ventral Aspect of Chief
Lymphatic Vessels of the Cat.
a. Axillary gland; as, pancreas Aselli; aft,
superficial lymphatics from the head; b,
bronchial glands receiving lymph from
lungs; c, lymphatic trunk; cr, cervical
glands; cv, laryngeal glands; d, vessel from
diaphragm; ej, external jugular vein; in,
inguinal glands; il, iliac glands; ju, junc-
tion of thoracic duct with tracheal trunk;
/, lumbar glands; It, large intestine; Iv,
lymph-vessel from liver; ?n, lacteal vessel
and glands of mesentery; n, superficial
lymphatics from limb; o, deep lymph-vessels
from limb; on, lymphatics from thoracic
wall; ol, vessel from abdominal wall; oc,
vessels from limb; rec, receptaculum chyli;
s, subclavian vein; /, lymphatics from skin
of leg; tr, tl, tracheal trunks; va, lymph
trunk from pancreas Aselli to thoracic duct;
V, superior vena cava; i and 2, submaxillary
lymph glands.

1 86

ELEMENTS OF MAMMALIAN ANATOMY

its openings into the external jugular vein near the common
jugular and jugulo-subclavian junctions. The caudal end of
the thoracic duct is expanded, forming the rcceplaculum chyli.
Numerous valves are present in the duct, and give to it a
moniliform or beaded appearance. It receives all the lymph

Fig. 92. — Photograph of Lymphatic Capillaries Injected with Berlin
Blue. They lie immediately beneath the skin on the outer aspect of the
ear.

a. Point of injection; the black area is Berlin blue lying in the connective-
tissue spaces from which the capillaries arise; n, injection escaped from ruptured
vessel.

from the left abdominal wall, both pelvic extremities, a large
part of the thoracic wall, and the thoracic and abdominal
viscera.

There is considerable variation in the number and position
of the lymphatico-venous connections in mammals. Usually,

THE VASCULAR SYSTEM 1 87

as in the cat, there are two openings in both the right and left
external jugular veins. However, the jugulo-subclavian tap
may be absent on one or both sides. Jugular lymph sacs
connecting the lymphatic and venous systems in the jugulo-
subclavian region have been described by Huntington and
McClure as usually present, more or less well-defined, in adult
cats. This interesting survival of an embryonic structure has
also been found in man and other mammals. In amphibians
and reptiles, lymph sacs and pulsating lymph hearts are normal
adult structures. In addition to the cervical communications
other venous taps may occur in the trunk region, as has been
shown by Silvester for monkeys and Job for rats. Lumbar
''taps" have also been found in cats. The significance of these
venous taps has been worked out by McClure and Silvester,
and more recently, in the rat, by Job.

DEVELOPMENT OF THE LYMPHATIC SYSTEM

The lymphatic system like the bloodvascular system is
developed in the mesenchyme by the enlargement and fusion of
intercellular spaces. According to Huntington and McClure
(Anat. Record, IX, 571) ''the development of the thoracic
ducts and the mesenteric lymphatics in the cat is correlated with
the degeneration of certain venous channels, many of which
are tributaries of the azygos division of the supracardinal veins.
A series of independent lymph spaces arise discontinuously in
the mesenchyme external to the intimal lining of these degenerat-
ing vessels and, as these lymph spaces gradually become con-
crescent to form continuous channels, the latter following a Une
of least resistance, utilize the static line vacated by these degen-
erating veins. This extraintimal replacement accounts for the
sinistral drainage plan finally assumed by the thoracic duct
system in the embryo of the cat." Not all of the lymph channels
are related to degenerating veins in this way. As a matter of
fact, perhaps the usual method of development is by the
concrescence of mesenchymal spaces independent of venous

1 88 ELEMENTS OF MAMMALIAN ANATOMY

■channels, as is found to be the case in lower vertebrates. The
theory that the lymphatic system is budded off directly from
the venous system is held by some investigators, however, the
theory outlined above seems best to agree with the results of
investigations in fishes (Allen, McClure), amphibians (Kamp-
meier) reptiles (Stromsten, Huntington) and birds (Miller).
The development of the lymphatic system is a very difficult
problem and much depends upon the kind of technique and its
interpretation. In the adult system as with the bloodvascular
system there are many variations, such as place and number
of lymphatico-venous taps, the persistence of lymph sacs (Fig.
84) or lymph plexuses etc. There are many problems relating
to the development, morphology and function of the lymphatic
system yet to be solved.

DUCTLESS GLANDS

The spleen, thyreoid gland, thymus gland, and suprarenal
(adrenal) bodies are ductless glands whose functions are imper-
fectly known. The largest of these is the spleen, which is
of a deep red color in a fresh specimen, and lies in the abdom-
inal cavity on the left side caudad to the stomach (Fig. 61).
It is about five centimeters long, two centimeters wide, and
less than a centimeter thick. It is composed of lymphoid
tissue of two forms, supported by connective-tissue trabeculae
which are merely prolongations of the enveloping capsule.
The two forms of tissue can be seen by cutting the organ trans-
versely. The dense lymphoid tissue appears as white spots
less than the size of a pin-head. They are the splenic nodules.
The intervening looser lymphoid tissue forms the greater part of
the spleen, and is known as the splenic pulp. The splenic artery,
a branch of the celiac axis, enters the spleen at its hilus and
divides into capillaries which terminate in irregular spaces,
thus permitting the blood to flow freely through the splenic
pulp, whence it is taken up by the capillaries of the splenic
vein leading to the portal vein. In embryonic life the spleen

THE VASCULAR SYSTEM 1 89

forms blood-corpuscles, but in post-natal life it seems to destroy
blood-corpuscles. An animal from which the spleen has been
removed may live many years in good health.

The thyreoid gland is composed of two parts lying on the
lateral aspects of the trachea, just caudad to the larynx. Each
part is less than two centimeters long. The two parts are
sometimes connected by a small isthmus extending ventrally
across the trachea, as in man. An enlargement of this gland
in man is called goiter. An animal can live only a short time
after the removal of the thyreoid unless it is fed thyreoids or
an extract of thyreoid gland. The function of the gland is to
supply iodin compounds and certain internal secretions to the

system.

The thymus gland is a median structure varying in size
according to age. In a cat about one-third grown it is very
large, extending craniad from the heart along the ventral
aspect of the trachea three or four centimeters. As the cat
grows older, it gradually dwindles, and is entirely absent in
aged specimens. Its function is unknown. It persists through-
out life in the lower vertebrates.

The suprarenal bodies are small, somewhat bean-shaped
organs lying craniad of the kidneys. An animal from which
they have been removed can live but a short time. They
give to the blood an internal secretion very essential to life.
A hormone known as adrenalin is one of the products, ''prob-
ably having to do with maintaining the proper tonus of the
muscle of the heart and blood-vessels thus underlying blood-
pressure." They are sometimes spoken of as suprarenal cap-
sules or adrenal bodies.

The above-named ductless glands occur in all mammals in
the same relative locations. The anatomy of the lymphatic
system is also similar throughout the various orders of mam-
mals. In some animals, especially man, the lymphatic glands
are more numerous than in the cat. The; tracheal trunks are
also wanting in man and a right thoracic duct about two centi-

190 ELEMENTS OF MAMMALIAN ANATOMY

meters long is usually present. A failure of the lymphatics
to do their work results in dropsy.

LABORATORY STUDIES AND SUGGESTIONS

1. Which of the four parts of the lymphatic system are visible in your
specimen?

2. Describe size and number of lymphatic glands in the mesentery.

3. Describe the location of lymph glands present in any other portion of your
specimen.

4. How do you distinguish a lymph gland from other glands?

5. \\hat causes the lymph to flow in one direction only?

6. What is meant by afiferent and efferent lymphatics?

7. Which kind of blood-corpuscles are found within the lymph-vessels?

8. From what regions does the thoracic duct receive the lymph?

9. What glands receive the lymph from the thoracic limb?

10. What glands receive the lymph from the pelvic limb?

11. Describe location of spleen, thyreoid and thymus glands, and suprarenal
capsules by naming the organs with which they are in contact.

12. Draw a cross-section of the spleen and label all features visible.

13. Draw a cross-section of the suprarenal body and label parts.

14. Tell what you know of the functions of the ductless glands."

15. What is a gland?

THE RESPIRATORY SYSTEM

Respiration is the process whereby the tissues are supplied
with oxygen and " relieved of their carbon dioxid. In mam-
mals, the special organs of respiration are the lungs, wherein
the carbon dioxid is received from the blood, while at the
same time the oxygen of the air passes through the thin-walled
capillaries to the red blood-corpuscles capable of conveying
it to the cells throughout the body. Each cell is composed
largely of carbon, hydrogen, oxygen, and nitrogen, and any
activity on the part of the cell is the result of the chemical
union of some of its elements, whereby several waste products
are formed, one of which is the gas, CO2 (carbon dioxid).
This gas is a poison and therefore must be eliminated. It
passes through the thin walls of the capillaries adjacent to
every cell, and is transferred through the veins to the heart
and thence to the lungs. Here the pulmonary artery di\ddes
up into capillaries ramifying over the air sacs (Fig. 95), thus
permitting the carbon dioxid to escape into the air sacs. Other
waste products resulting from chemical acti\aty within the
cells are carried away by the kidneys and sweat glands.

The respiratory system consists of the nasal passages,
pharynx, larynx, trachea, and lungs. The air taken in at the
anterior nares is warmed in passing over the mucous mem-
brane of the turbinated bones, after which it goes on through
the posterior nares (Fig. 18) to the pharynx, and thence into
the larynx.

The larynx is the cartilaginous expansion of the cranial end
of the trachea, at the base of the tongue. The basihyal bone
is attached to the cranial ventral margin of the larynx and on
each side is a thyreohyal bone (Fig. 21). Dorsal to the larynx
is the esophagus. By removing carefully the muscles and

191

192

ELEMENTS OF MAMMALIAN ANATOMY

fibrous tissue from the cartilage the larynx is seen to be com-
posed of five pieces: the epiglottis, thyroid cartilage, two ary-
tenoid cartilages, and the cricoid cartilage (Fig. 21). The
epiglottis is the small triangular cartilage that closes the glottis
when food passes into the esophagus (Fig. 62). The thyreoid
cartilage constitutes the largest part of the larynx. In man it
forms the prominence known as Adam's apple. Dorsally the

Fig. 93. — Diagrammatic Transverse Section of the Chest.
ao. Aorta; br, bronchus; crd, spinal cord; esoph, esophagus; hd, head of rib;
pa, parietal pleura; pc, cavity of the pleura; sp, spinous process; st, sternum;
tb, tubercle of rib; tr, transverse process; vp, visceral pleura; /, thoracic duct;
n, sympathetic nerve cord; as, azygos vein; trc, trachea; v, pulmonary veins.

two halves of the thyreoid cartilage are separated, each pro-
jecting craniad into a process known as a cornii. The arytenoid
cartilages are the two small paired pieces caudad to the thy-
reoid, on the dorsal side. The cricoid cartilage forms a com-
plete ring at the caudal end of the larynx (Fig. 21).

There are a number of ligaments connecting the various
parts of the larynx, the most important of which are the vocal
cords. These are of two kinds — true and false. They are
best demonstrated by dividing the larynx, sagittally. The
superior or false vocal cords are the two superior thyreo-ary-

THE RESPIRATORY SYSTEM

193

Fig. 94. — Photograph of a Lung Corrosion of a Puma in Morphologic
Museum of Princeton University. The specimen was prepared by Mr.
Sylvester. The trachea with all its ramifications was injected with white paraf-
fin, and the pulmonary artery with red paraffin, after which the lung substance
was eaten away with acid.

tr. Trachea; hr, bronchus; h, bronchial tube; c. bronchiole. The pulmonary
artery and its branches are much darker than the air tubes.

194 ELEMENTS OF MAMMALIAN ANATOMY

enoid ligaments passing from the arytenoid to the thyreoid
cartilage, at the base of the epiglottis. The cat is said to
use these cords in purring. The inferior or true vocal cords
are the inferior thyrco-arytenoid ligaments, consisting, as in
man, of a fold of mucous membrane on either side, just caudad
to the false vocal cords (Fig. 62). The depression on either
side between the true and false vocal cords is the ventricle.
By means of the muscles attached to the arytenoid and thy-
reoid cartilages, the tenseness of the vocal cord is regulated,
and the various pitches of voice produced.

The trachea, or windpipe, is the tube leading from the larynx
to the lungs (Fig. 61). Its walls are prevented from collapsing
by the presence of about forty-five cartilaginous rings which
are incomplete dorsally. Before passing into the lungs the
trachea bifurcates into a right and a left bronchus. The
trachea and bronchi are lined by ciliated columnar epithelium.
The cilia project freely into the lumen from the columnar walls,
and are always waving in such a manner as to carry the secreted
mucus lodged thereon toward the mouth, thereby preventing
the lungs from becoming clogged with foreign material. Cili-
ated cells with the cilia in action may be easily demonstrated
by scraping very lightly a little mucus from the posterior part of
the roof of the frog's mouth, and mounting the same in a drop of
saliva on a glass slip, which is then to be examined with a
microscope magnifying about 300 diameters. The diaphragm
of the microscope should be arranged so as to admit but little
light.

The lungs together with the heart fill up the greater part of
the thoracic cavity. In a cat recently killed the lungs may be
expanded by tying a piece of glass tubing on the trachea and
blowing into it strongly for a few seconds. Each lung is com-
pletely invested by a sac of delicate transparent serous mem-
brane called pleura (Fig. 93). Each sac is reflected at the root
of the lung, where the blood-vessels and bronchus enter, so as
to form a parietal layer lining its half of the thoracic cavity.

THE RESPIRATORY SYSTEM 1 95

The median space between the two sacs is called the media-
stinum. The anterior or ventral mediastinum contains blood-
vessels and the thymus gland. The dorsal or posterior medi-
astinum lodges the trachea, esophagus and aorta and the heart
occupies the middle mediastinum.

Each lung is divided by deep clefts into several lobes. The
left lung is composed of two large lobes and a small one. The

Fig. 95. — Diagram Showing Structure of the Lung on the Cat. (Modified

after Miller.)

A, Artery; B, bronchiolus; B.R, respiratory bronchiole; D.A, alveolar duct; a,

atria; A.S, alveolar sac; A.P, pulmonary alveolus; V, vein.

right lung consists of four unequal lobes. The cranial end of
the lung is the apex and the caudal end, resting against the dia-
phragm, is the base. The bronchi, as they are continued into
the lungs, subdivide into smaller tubes, whose later subdivisions
are the bronchioles. The latter, dividing like the branches of
a tree, finally terminate in blind pouches known as infundihula
or alveoli, the wall of which are thickly beset with microscopic

196

ELEMENTS OF MAMMALIAN ANATOMY

sac-like evaginations named air sacs (Figs. 94 and 95). The
walls of these air sacs are very thin, somewhat like the perito-
neum. Over them course numerous thin-walled capillaries, so
that the carbon dio.xid of the blood passes out into the air as

Fig. 96. — Photograph of Human Heart and Lungs from Ventral Aspect.

a, Aorta; /, trachea.

the oxygen passes into the blood. Expiration is the process of
forcing the air out of the lungs which have been filled by an
inspiration chiefly effected by depressing the diaphragm and
elevating the ribs. The two processes together are spoken of
as a respiration.

THE RESPIRATORY SYSTEM 197

LABORATORY STUDIES AND SUGGESTIONS

1. Of what four elements are the soft parts of the body largely composed?

2. What waste gas is formed in every part of the body exercised?

3. Through what three channels do waste materials pass from the blood?

4. Describe the manner in which the oxygen of the air reaches the blood?

5. Write a description of the pharynx.

6. Bisect the larynx in the sagittal plane, make a drawing of the cut aspect,
and label all features.

7. How many cartilaginous rings in the trachea and what is their use?

8. Describe as much of the pleura as can be seen in your specimen.

9. Do the right and left bronchi have the same number of main branches?

10. Why do the air cells seldom become clogged?

11. What muscles are largely used in respiration?

12. Describe the hyoid bone as seen from your dissection.

13. What part of this bone can 3'ou feel beneath your mandible?

14. How does the carbon dioxid given off by the cells in the foot reach the
lungs?

15. What causes the air to enter the lungs?

16. Inflate the lungs of a freshly killed animal by forcing air from your lungs
into a glass tube tied into its trachea.

17. After retaining a full inspiration of air as long as possible, expire it through
a glass tube into the bottom of a two-liter bottle and insert into the bottle a
lighted splinter.

18. Describe the pulmonary circulation.

THE EXCRETORY AND REPRODUCTIVE

SYSTEMS

As explained in the last section, a portion of the waste prod-
ucts produced by the activity of the cells of the body is passed
off through the lungs, but some other outlet must be provided
for the excretions that are not in the form of gases. These
liquid excretions, containing various salts and urea, pass off
through the kidneys and the glands of the skin.

The latter are of two kinds, sudoriferous or sweat glands, and
sebaceous or oil glands, with ducts opening into the hair follicles
near the surface. The sweat glands lie deeper than the seba-
ceous glands. The former are subcutaneous and consist of a
more or less coiled tube with a straight duct opening on the
surface. They are most abundant on the tip of the nose and
the balls of the feet. The sebaceous glands are very numerous
all over the body. Both are of microscopic size.

A still more important part of the excretory system is the
urinary system, consisting of the kidneys, two ureters leading
from the kidneys to the bladder, the bladder, and the urethra.

The student should note that the kidney is not enveloped by
the peritoneum, like the other abdominal organs, but lies dorsad
to it and is encased by a fibrous covering known as the capsule.
The hilus is that portion of the concave surface where the renal
artery and vein and ureter enter. A median longitudinal sec-
tion of the kidney will show that the ureter within the kidney
enlarges, forming the pelvis, into which projects the renal
papilla (Fig. 98). This is better demonstrated in a transverse
section.

The substance of the kidney is composed of an outer cortical
layer, about a half centimeter thick, and an inner medullary
substance adjacent to the pelvis, and projecting into the latter

198

EXCRETORY AND REPRODUCTIVE SYSTEMS

199

in the form of a papilla. In the cortical substance are hundreds
of renal corpuscles, each composed of a ball of capillaries (Fig. 99)
enveloped by the invaginated enlarged extremity of a tubule
which carries away the urine by a tortuous course to the papilla
(Fig. 99). In the renal corpuscles the water and other mineral
substances of the urine are extracted from the blood by means
of the epithelial cells forming
the inner wall of the capsule
of Bowman. These urinary
products pass through the
proximal convoluted tubule and
the loop of Henle to the distal
convoluted tubule, where they
are mingled with the urea ex-
tracted from the blood by the
columnar epithelial cells of the
tubule. From this point the
excretions flow into the collect-
ing tube which empties into the
pelvis at the papilla. In a pre-
pared microscopic section of the
kidney, these renal corpuscles
and renal tubules may be seen
with a microscope magnifying
about 200 diameters.

The ureter is a small tube
leading from the pelvis of each
kidney along the dorsal aspect
of the abdominal cavity to the
dorsal and caudal end of the
bladder.

The bladder is the sac for re-
taining the urine. Itliesventrad

to the rectum, a little to the right of the median line, being held
in place by the ligamentum suspensorium, a fold of the perito-

FiG. 97. — Ventral Aspect of Fe-
male Urino-genital System with
THE Bladder Pulled to One Side.

a. Entrance of the urethra into the
vestibule; ao, aorta; bl, bladder; cl,
clitoris; en, cornu or horn of the
uterus; fl. Fallopian tube, the left
one is cut off; fm, fimbriated ex-
tremity of the Fallopian tube; kd,
kidney; /, ovarian ligament; ov,
ovary; ra, renal artery; rv, renal
vein; re, rectum; ur, ureter; ut, body
of the uterus; uth, urethra; vc, vena
cava; vg, vagina; vs, vestibule.

200

ELEMENTS OF MAMMALIAN ANATOMY

neum attached to the mid-ventral line. It is also attached
by lateral ligaments. On its dorsocaudal aspect near where
the ureters empty, the urethra originates and passes along the
ventral surface of the vagina to the vestibule, within which it
opens (Fig. 97). In the male it
passes directly from the bladder
along the ventral surface of the
rectum to the root of the penis at
the pubic symphysis, and thence on
through the corpus spongiosum to

Fig. 98. — Median Longitudinal Section'of
A Kidney.
cor. Cortical substance; hi, hilus; tned,
medullary portion; p, papilla; pi, pelvis; n,
pyramids; ur, ureter.

the point of the penis. The ureter.

formed by mucous membrane.

THE FEMALE REPRODUCTIVE
SYSTEM

The female reproductive organs

Fig. 99. — Diagram of the
Structure of the Kidney
between the Lines a and c
IN Fig. 98.

ar. Arteries leading to the
renal corpuscles, only one
capsule being shown; h, veins
leading from the capillary

bladder, and urethra consist largely network about a convoluted

^ , . ,,..,. tubule as at n\ ex, line mark-

of muscular tissue, the Immg bemg i^g the boundary between the

cortical and medullary por-
tions of the kidney; cp, cap-
sule of Bowman enveloping
the bunch of capillaries; d,
distal convoluted tubule; hi,
Henle's loop; n, capillary net-
work about the tubule; /, the
bunch of capillaries of Mal-

are the two ovaries^ a pair of uterine pighian tuft; ur, portions of

. , , I . renal tubules emptying into

tubes, a uterus, and a vagina. lo ^he collecting tubule c; xc,
demonstrate these, the entire ventral proximal convoluted tubule.
abdominal wall must be removed and the pubic symphysis
severed with the bone-cutters. The ovaries are the small yel-
lowish oval bodies about one centimeter long lying just caudad of

EXCRETORY AND REPRODUCTIVE SYSTEMS 20I

the kidneys, against the dorsal abdominal wall. From the vicin-
ity of each extends a tube caudad to join its fellows in the median
line ventrad to the rectum (Hgs. 6i and 97). The cranial por-
tions of these are the uterine tubes, and the larger caudal portions
are the cornua of the uterus. The junction of the cornua in
the median line forms the body of the uterus.

The uterine tube is smaller in diameter than the cornu of the
uterus, generally more or less contorted, and terminates by a
fimbriated expansion or mouth opening freely into the
abdominal cavity.

The uterine tubes and uterus are suspended by the broad
ligament, or ligamentum latum, which is a fold of the perito-
neum attached to the dorsal abdominal wall. The round liga-
ment, or ligamentum rotundum, also aids in keeping the uterus
in place. This appears as a thickening of the broad ligament
when the latter is looked through toward the light. The round
Hgament extends from about the middle of the horn or cornu of
the uterus ventrad of Poupart's ligament, and through the mus-
cles of the abdominal wall beneath the skin of the inguinal
region, where it gradually loses itself. It is exceedingly delicate
and thread-like. During pregnancy a portion of the uterine wall
becomes very vascular and undergoes other important changes.
It unites with the chorion of the fetus to form the placenta.
The blood-vessels of both parts of the placenta, maternal and
fetal, interlace but do not directly communicate with each other.
It is through the placental blood-vessels that the fetus receives
its nourishment and oxygen.

The vagina extends from the uterus to the vestibule, opening
on the surface ventrad to the anus. The small papilla just
caudad of the orifice of the urethra on the ventral surface
of the vestibule is the clitoris, the homologue of a part of the
penis in the male. The prominent circular fold of mucous
membrane craniad of the orifice of the urethra represents
the hymen, which marks the separation between the vagina
and vestibule. This structure may be shown by making a

202 ELEMENTS OF MAMMALIAN ANATOMY

median longitudinal section through the vagina. Bartholin's
vestibular glands lie on the lateral aspect of the vestibule, into
which their ducts open. Each one is about the size of a small
pea. The vagina, uterus, and uterine tubes are lined with
mucous membrane in which are many glands. The mucous
lining is surrounded by a muscular coat especially thick in the
uterus.

The ovaries are the organs producing the female germ cells
or ova which when fertilized are known as the eggs (Figs. 6i
and 97). One lies caudad of the kidney on each side and is
invested by peritoneum, which should be carefully dissected

Fig. 100. — Section of Ovary. X 40.
sr. Surface of the ovary; gr, Graafian follicle with mature ovum; o, ovum;
c, cavity of the follicle; un, undeveloped ova; sirm, stroma or connective ele-
ments of the ovary; m, membrana granulosa; d, discus proligerus (cumulus
oophorus).

away. A microscopically prepared section of the adult ovary
magnified about 100 diameters will reveal a number of ova in
a more or less mature state. Usually a peripheral ring of
very young ova is present, more mature ones are near the center,
while one or two quite ripe ova are very near the circum-
ference. As the ova develop, a follicle or sac known as the
vesicular follicle (Graafian follicle) is formed about them. This
is lined with several layers of epithelial cells forming the stratum
granulosum. At one side of the follicle the stratum granulosum
thickens and envelops the ovum, forming the cumulus oophorus.
The cavity of the follicle is filled with liquor folliculi. When
the ovum becomes almost mature, the walls of the follicle have
grown peripherad, so as to cause a pin-head protuberance on
the surface of the ovary clearly visible to the naked eye. In a

EXCRETORY AND REPRODUCTIVE SYSTEMS 203

fresh specimen this protuberance may be picked open and the
ovum expelled on a slide for examination with the microscope.
The ovum is scarcely visible to the unaided eye. The human
ovum is still smaller.

The ova of all mammals, except the duck-bill and spiny
ant-eater, are very small. When the ovum becomes mature,
the protruding wall of the follicle bursts, permitting its con-
tents to be received by the expanded end of the uterine tube,
whence it passes to the uterus. If the male element, the sper-
matozoon, enters the ovum, the latter is soon enveloped by a
growth of mucous membrane and retained in the uterus for
development. Ripe ova occur near the close of the first year
of the cat's life and new ones probably continue to mature
during the next ten years. The discharge of the ova from the
ovary is accompanied by a constitutional disturbance, during
which an extra amount of blood is sent to the sexual organs,
and the sexual appetite becomes very marked. In the human
species this disturbance occurs about every twenty-eight days.
Mature ova occur in the human ovary between the thirteenth
and forty-eighth years.

The mammary glands of the adult female cat reach their
full development when it gives h)irth to young. They may
be seen by carefully removing the skin from the ventral aspect
of the body, when they will appear somewhat like a thin layer
of adipose tissue extending from near the axilla to the pubic
symphysis. There are four teats or nipples on each side. In
some mammals the nipples are less numerous and confined
either to the thoracic or inguinal region. In the elephant,
Chiroptera, and Primates there are but two nipples, and they
are thoracic. In most Ungulates the nipples are inguinal.
THE MALE REPRODUCTIVE SYSTEM

The organs of generation in the male consist of the testes,
the ducts leading from the testes to the urethra, the prostate
gland, hulbo-urethral glands (Cowper's gland), and the penis.

204

ELEMENTS OF MAMMALIAN ANATOMY

The testes are two in number, contained in a pouch of

integument called the scrotum,
which hangs beneath the anus.
Internally the scrotum is di-
vided into two chambers. By
dissecting away the adipose
tissue covering the spermatic
cord in the inguinal region
(Fig. 57) it may be seen that
the cord and the testes are en-
veloped by a tough sheath.
This is composed of cremasteric
fascia derived from the apo-
neurosis of the external oblique
muscle, and of the tunica vag-
inalis.

During the fetal life the
testes lie in the abdominal
cavity, and when they descend
into the scrotum about the
time of birth, a double layer
of peritoneum is pushed down
before them through the in-
guinal canal, forming a diverti-
culum whose blind end lies
within the scrotum, while the
constricted portion forms a
channel for the vas deferens,
spermatic nerve, and vessels.
These three structures form
the spermatic cord (Fig. 57).
The fascia propria (tunica vag-
inalis communis) is insepara-
bly united with the adjacent
parietal layer of the peri-

FiG. loi. — Ventral Aspect of the
Male Reproductive Organs.
cr. One of the crura of the penis;
ep, epididymis revealed by cutting
and reflecting; vg, a piece of the tunica
vaginalis and albuginea; et, external
abdominal ring; it, internal abdominal
ring; in, inguinal canal; g, glans penis;
gd, Cowper's bulbo-urethral glands;
pe, penis; pr, prostate gland; re,
rectum; /, testis from which the
tough sheath composed of the levator
scroti muscle and cremaster fascia
has been removed, leaving it en-
veloped by the tunica vaginalis; ts,
testicle from which a portion of the
tunica vaginalis and albuginea has
been reflected; uth, urethra; ur, ur-
eters; vd, spermatic cord; vdd, vas
deferens within the abdominal cav-
ity; vg, tunica albuginea reflected;
vg2, tunica albuginea; v, spermatic
vein.

EXCRETORY AND REPRODUCTIVE SYSTEMS 205

toneum. The visceral layer of peritoneum is quite delicate
and transparent and lies close to the testis. Within the tunica
vaginalis, is the tunica albuginea, closely investing the testicle
and adjacent to the epididymis, penetrating the substance of
the gland, forming a septum known as the mediastinum testis
or corpus Highmori (Fig. loi).

The testis is about ij^ centimeters long by i centimeter
thick. On its dorsal surface lies the epididymis, an elongated
body composed of an enlarged extremity,
the globus major, and an attenuated por-
tion, the globus minor. The main por-
tion of a testicle is composed of many
minute coiled tubules, tubuli seminiferi,
which unite into a few tubules near the
surface of the testis beneath the globus
major, into which they extend. These

, , 1 7 7' /r • ^^^- 102. SpERMA or

tubules are the auctuii ejjerentes testis, male Germ Cells.
The epididymis is composed of a single ^ ^T'h d- / tail
greatly convoluted tubule of which the
ductus deferens is a continuation. The latter proceeds
craniad to the external abdominal ring, which it enters to
traverse the inguinal canal into the abdominal cavity. It
then curves caudad and enters the urethra on its dorsal as-
pect in the region of the prostate gland.

The inguinal canal begins with the external abdominal ring,
which is an opening in the tendon of the external oblique
muscle, and ends with the internal abdominal ring, which is an
opening in the fascia of the transversalis muscle (Fig. 56).
By accident, a fold of the small intestine in man sometimes
descends through the inguinal canal, which condition is known
as hernia or rupture.

The penis is a cylindrical pointed body about three centi-
meters long when in repose. It is composed of two kinds of
tissues arranged in three bundles. The corpus spongiosum is
the median ventral bundle, extending throughout the length

2o6 ELEMENTS OF MAMMALIAN ANATOMY

of the organ, and at the end forms the glans or head. The
two dorsal lateral bundles are the corpora cavernosa. They
form the greater part of the penis proximad of the glans, and
by diverging somewhat before their attachment on either side
to the pubis and ischium form the crura. The penis is sus-
pended from the wall of the abdomen by a fold of integument
inserted at the base of the glans, and forming the prepuce.
The latter is a free projection of skin covering the glans. In
the midst of the penis is a small bone. The penis is the organ
of copulation, and is composed of a spongy mass of elastic and
muscular fibers richly supplied with highly distensible blood-
vessels which when filled render the organ erect.

The prostate gland surrounds the urethra dorsally and lat-
erally about two or three centimeters from the bladder. This
gland secretes a milky fluid which is poured into the urethra
through many ducts, during copulation, and serves as a medium
for the spermatozoa (Fig. loi).

Cowper's bulbo-urethral glands are two in number, about
the size of a pea, and lie in the angles formed by the urethra
and the crura of the corpora cavernosa. These glands secrete
an alkaline viscid fluid of unknown function, "but which may
be to neutralize any acidity of the urethra which might in-
hibit the activity of the spermatozoa" (McMurrich). One
duct from each gland opens into the urethra.

REMARKS ON THE MAMMALIAN UROGENITAL SYSTEM

The urogenital system is subject to some variations in the
different orders of Mammalia. In the Ornithodelphia, the
mammary glands are devoid of teats and the oviducts corre-
sponding to the Fallopian tubes and horns of the uterus do not
unite in the median line to form the body of the uterus, but
unite with the urethra, forming the urogenital canal. The
latter opens into an enlarged terminal portion of the rectum,
called the cloaca. The ureters also open directly into the
cloaca, so that there is but one external opening for the genital

EXCRETORY AND REPRODUCTIVE SYSTEMS 207

and excretory products. In the above features the Mono-
tremes resemble the Amphibia and reptiles. All mammals are
viviparous except the Monotremata, which are oviparous, lay-
ing eggs as large as those of the robin. The Ornithorhynchus
incubates its eggs in an underground nest, while the Echidna
carries her single egg in a temporary abdominal pouch.

The Marsupialia bring forth their young in a very immature
condition. They are then carried for several months in an
abdominal integumentary pouch, the marsupium, within which
are the nipples. In the Monotremata, Cetacea, Sirenia, and
elephant the testes do not descend into a scrotum, but are
retained in the primitive location within the abdomen. In
Primates and some Edentates, the uterus is merely a pear-
shaped body without any cornua, the uterine tubes leading
directly into the body of the uterus.

In the ox, bears, seals, and cetaceans the kidneys are dis-
tinctly lobulated. Internal evidence of lobulation is presented
in most mammals by the renal papillae. In the embryo, the
kidneys of all mammals are lobulated.

LABORATORY STUDIES AND SUGGESTIONS

1. What other waste products besides CO2 result from the chemical action
in the tissues of the body?

2. Write a description of all parts of the urinary system visible in your
dissection.

3. Bisect a kidney longitudinally in the horizontal plane, draw the cut
surface, and label all features.

4. Explain the parts of a renal tubule.

5. Wherein does the male urinary system differ from the female?

6. Make a drawing of the uterine tubes and uterus and label all parts.

7. Describe location, size, external appearance, etc., of the ovary as seen in
your specimen.

8. How are the female reproductive organs held in place?

9. Can you distinguish externally the termination of the uterus and the begin-
ning of the vagina?

10. Are there any eggs protruding from the ovary or any cavities from which
eggs have been recently discharged?

11. Describe a Graafian (vesicular) follicle.

12. What must be added to the ovum to produce another animal?

2o8 ELEMENTS OF MAMMALIAN ANATOMY

13. Name the parts of the male reproductive system present in your specimen
and locate them.

14. Describe the course of the spermium from the testis to the exterior.

15. Do all mammals nourish their young in the same manner?

16. What mammals incubate their eggs externally?

THE NERVOUS SYSTEM

The nervous elements of the cat form three systems, known
as the central, peripheral, and sympathetic. The central nervous
system includes the brain and spinal cord. The peripheral
system includes the twelve pairs of nerves emanating from the
brain and the forty pairs of nerves emanating from the spinal
cord to supply the extremities and trunk. The sympathetic
system is composed of two ganglionated nerve cords extending
throughout the trunk within the body cavity, one on either
side of the vertebral column, and their various branches to all
the viscera, blood-vessels, etc., of the body (Figs. 105 and 106).

THE BRAIN

The central nervous system is known as the cerehro-spinaJ
axis. It is composed of the brain and spinal cord. The brain
lies within the cranial cavity and is protected by three mem-
branes called the meninges. These may be demonstrated by
cutting away the roof of the skull with the bone forceps. The
dura mater is the tough fibrous membrane lining the interior of
the skull. It dips down between the two halves of the cerebrum,
forming the/a/o; cerebri. Between the cerebrum and cerebellum
in the cat it is ossified, thus forming the bony shelf or tentorium
cerebelli (Fig. 19). The second membrane of the brain is the
arachnoid. Between the dura mater and the arachnoid is
the subdural space, containing a fluid having the nature of the
aqueous humor. The arachnoid is a very delicate membrane
which does not dip down into the clefts between the folds of the
brain, as is the case with the pia mater, but passes across these
depressions, where it may be easily demonstrated (Fig. 109).

The subarachnoidal space lies between the arachnoid and pia
mater. The pia mater is the delicate vascular membrane follow-

209
14

2IO ELEMENTS OF MAMMALIAN ANATOMY

ing SO closely the folds and clefts of the brain that it becomes
apparent only when lifted carefully by the forceps.

In order to study the brain satisfactorily each student should
have a specimen hardened according to directions on page 14,
and also should be permitted to examine a series of sections cut
transversely about a centimeter thick. The brain of a calf or
sheep serves the learner's purpose better than that of a cat, as
the parts are larger, and they are also easier to procure. An
additional advantage is also found in the fact that there is some
difference between the brains of the cat and calf, and the
student must therefore rely more on his own observations.

External Features.^ — The brain is composed of five parts:
the medulla oblongata, or myelencephalon; the pons Varolii and
cerebellum, forming the meiencephalon; the corpora quadri-
gemina and crura cerebri, composing the mesencephalon; the
diencephalon, including the optic thalami and other parts
bounding the third ventricle; and the telencephalon, or cerebral
hemispheres. The medulla oblongata, sometimes called the
bulb or stem of the brain, is the expansion of the spinal cord as it
passes through the foramen magnum. The pons Varolii is the
bridge of transverse fibers seen on the ventral aspect of the
brain just craniad of the medulla (Fig. 104). The cerebellum or
little brain lies on the dorsal side of the medulla and is partly
covered by the caudal part of the cerebrum. The mesencephalon
is not visible externally on the dorsal aspect, but may be seen
immediately craniad of the cerebellum by cutting away the
cerebrum (Fig. 107). The diencephalon is visible externally only
on the ventral aspect of the uncut brain, where it forms the floor
of the third ventricle. It may be viewed as a whole if the dorsal
half of the cerebrum including the corpus callosum is cut away.
The telencephalon or end brain is composed of the two large
hemispheres partially surrounding the diencephalon and
mesencephalon.

The brain is composed of two kinds of matter, white and gray.
The former is constructed for the most part of fibers, while the

THE NERVOUS SYSTEM

211

latter is formed largely of cells. The outer or cortical portion
of the cerebrum and cerebellum is a layer of gray matter less
than a half centimeter thick, and is disposed in folds called
gyri or convolutions with intervening slit-like depressions termed
sulci, the most important of which are called fissures.

The four different portions of
the cerebrum are known SiS frontal,
parietal, occipital, and temporal
lobes, which occupy the respective
regions of the cranial cavity. The
frontal and parietal lobes are
separated by the crucial fissure,
extending transversely between
them. The olfactory lobe (usually
torn off in removing the brain from
the skull) projects from the cranial
portion of the frontal lobe. The
parietal lobe is marked by three
gyri, named according to location
gyrus marginalis, gyrus, supra-
sylvius, and gyrus ectosylvius
(Figs. 103 and 104). The caudal
portions of the gyri marginalis
and suprasylvius constitute a
portion of the occipital lobe.
These two gyri are separated by
the lateral sulcus. The supra-
sylvian sulcus extends between
the gyrus suprasylvius and the
gyrus ectosylvius. The splenial

sulcus (Fig. 106) separates the gyrus marginalis from the gyrus
fornicatus on the medial aspect of the parietal and occipital
lobes. There are no definite sulci or fissures separating
the parietal, occipital, and temporal lobes. The postrhinal fis-
sure, extending caudad from the fissure of Sylvius, divides the
temporal lobe into two portions on the ventral aspect.

Fig. 103. — Dorsal Aspect of
THE Brain.
a. Gyrus marginalis; ac, white
matter of the cord; ad, gray mat-
ter of the cord; b, gyrus supra-
sylvius; c, gyrus ectosylvius; cr,
crucial fissure; ce, lateral lobe of
cerebellum; d, lateral sulcus; e,
suprasylvian sulcus; Ig, great
longitudinal fissure; md, medulla
oblongata; n, first spinal nerve; ol,
olfactory lobe; p, posterior pyra-
mids; sp, spinal cord; v, vermis
of cerebellum.

212 ELEMENTS OF MAMMALIAN ANATOMY

The ventral surface (Fi^. 104) of the brain also presents impor-
tant features which should be noted by the student before
investigating the internal structure. The anterior pyramids,
two indistinctly difTerentiated bundles of fibers, occupy the
middle of the ventral region of the medulla, and craniad of the
pons help form the peduncles of the cerebrum. Laterad of
each pyramid is the olivary projection. A broad band of trans-
verse fibers appearing just caudad of the pons Varolii and lateral
of the anterior pyramids is the corpus trapezoideiim.

The pons Varolii is itself composed of a band of transverse
fibers which on either side forms the middle peduncle of the
cerebellum. The fibers originate either in cells of the medulla
or those of the cerebellum.

The crura cerebri, or peduncles of the cerebrum, the ventral
portions of which are continued as the anterior pyramids (Fig.
104), are seen just craniad of the pons. Their fibers unite the
cerebrum to the rest of the brain and the spinal cord. In the
space between the crura and the optic chiasm is a prominent
projection, the terminal nodular portion of which is the pituitary
body or hypophysis. It occupies the hypophyseal fossa of the
skull and is usually torn off in removing the brain. Caudad of
the hypophysis are two small rounded white bodies, the corpora
mamillaria. The tuber cinereum, a slightly elevated mass
of gray matter behind the optic chiasm, bears on its surface
the funnel-shaped stalk, the infundibulum, to which the
hypophysis is attached. If the two latter parts are removed,
there is seen a small elongated aperture through the tuber
cinereum into the third ventricle (Figs. 104 and 106).

The optic commissure, or optic chiasm, is the commissure
formed by the crossing of the optic nerves just craniad of the
tuber cinereum. The prolongation of the optic nerves dorsad
from the optic commissure forms the optic tracts, partly covered
by the temporal lobes. On either side of the median fissure
just craniad of the optic chiasm is a somewhat triangular area
known as the anterior perforated space because of the numerous
vessels that enter the brain in this region. Laterally this space

THE NERVOUS SYSTEM

213

Fig. 104. — Ventral Aspect of the Brain.

2, 3, 4. 5, 6, 7, 8, 9, 10, II, 12, The cranial nerves; a, ophthalmic branch of the
trigeminal nerve; an, anterior pyramids; at, anterior horn of gray matter; h,
superior maxillary branch of the trigeminal nerve; iia, eleventh cranial nerve
with roots from the spinal cord; c, mandibular branch of the trigeminal nerve;
ca, corpus mamillare; ch, cerebellum; cc, canalis centralis; en, cornea; ct, cut
surface of spinal cord; ex, external rectus muscle; cr, peduncle of the cerebrum;
g, Gasserian ganglion of the trigeminal nerve; hi, pyriform lobe; in, opening
into the tuber cinereum revealed by removal of the infundibulum and hypophy-
sis; i, internal rectus; to, inferior oblique; ir, inferior rectus; «i and ni, first and
second spinal nerves; ol, olfactory lobe; op, optic commissure; ol, optic tract;
p, posterior horn of gray matter; pt, anterior perforated space; pv, pons Varolii;
r, medial or inner root of olfactory nerve; rt, lateral root of olfactory nerve;
pr, postrhinal fissure; sy. Sylvian fissure; s, superior rectus muscle; /s, corpus
trapezoideum; x, external arciform fibers.

214 ELEMENTS OF MAMMALIAN ANATOMY

is bounded by the lateral olfactory tract or lateral root of the
olfactory nerve, which presents the appearance of a band of
white libers extending from the olfactory lobe into the temporal
lobe. The medial or inner root of the olfactory nerve is seen
adjacent to the median ventral line craniad of the anterior
perforated space. The olfactory lobes project from the cranial
ventral portion of the cerebrum and give origin to the first pair
of cranial nerves.

Internal Structure.- — The canalis centralis, a small canal
extending throughout the center of the spinal cord, enlarges
in the region of the brain, forming four cavities or ventricles
communicating with each other by narrow channels. The
brain is therefore to be considered as a hollow structure. The
first and second ventricles, also known as lateral ventricles, occupy
the cerebral hemispheres (Fig. 105). The third Sind fourth ven-
tricles lie in the median line, and are therefore well seen in a
sagittal section of the brain (Fig. 106).

The Ventricles of the Brain. — The fourth ventricle is visible
on the dorsal aspect of the medulla oblongata (Fig. 106). It
is about three centimeters long by one centimeter wide, and
lies ventral to the cerebellum. This ventricle is merely an
expansion of the canalis centralis of the spinal cord. Its roof
is very thin and consists of two portions, one of which, the
superior medullary velum, sometimes called the valve of Vieus-
sens, covers the cranial half of the ventricle, the other portion
is the inferior medullary velum, lying over the caudal half.
The latter velum is composed of a fold of pia mater tucked in
between the cerebellum and medulla, in addition to a layer of
epithelial cells on the ventricular aspect of the pia mater.
Some nervous matter in addition to the pia mater and epithe-
lium forms the superior velum. Two longitudinal vascular
fringes hanging from the roof of the ventricle on either side of
the mid-line, form the choroid plexus, which is merely a network
of blood-vessels carried by a reflected portion of the pia mater.
The choroid plexus appears to be the main source of the cere-
brospinal fluid.

THE NERVOUS SYSTEM 215

Craniad the fourth ventricle is continued as a small canal,
the iter, or aqueduct of cerebrum, which lies ventrad to the
corpora quadrigemina and opens into the third ventricle (Fig.
106). The latter is a narrow, vertical, cleft-like space between
the optic thalami. The two thai ami are united by the soft
or middle commissure, better designated
as the massa intermedia, extending
through the ventricle. Unless this
ventricle has been injected with a starch
mass through the infundibulum before
the brain was hardened, its cavity will
not exceed a millimeter in width. The
roof is formed much in the same manner
as that of the fourth ventricle, by a ^^^ ios.-Diagram of

reflection of the pia mater lined with Ventricles of the Brain

. , „N . Viewed Dorsally.

epithelmm (rigs. lOO and I05j. A ah. Anterior horn of the

sagittal section of the brain placed in a ^^^^^^^f "^^ rrebrum- cc.'

pan of water will show the fold of pia canalis centralis of the spinal
n 1 7 ' , . ', cord: 3 and 4, third and

mater called velum tnterposttum ex- ^^^^^^^^ ventricles; w, fora-
tending craniad from the pineal gland, "^^n of Monro; mi, middle

° . horn or cornu of the ven-

Two folds of the pia mater hanging on tricie.
either side from near the median line

form the choroid plexus as in the fourth ventricle. The body
of the fornix lies dorsad of the membranous roof of the ven-
tricle. In the floor lie the corpora mamillaria, the infundibu-
lum, the tuber cinereum, and the optic commissure. Craniad
the third ventricle communicates with the lateral ventricles
by silt-like apertures, the interventricular foramina of Monro,
passing laterad and ventrad of the anterior pillars of the fornix
(Figs. 106 and 107).

The lateral ventricles are found in the cerebral hemispheres
ventrad to the corpus callosum. They are the largest ven-
tricles of the brain. In order to view them satisfactorily, the
entire dorsal portion of the brain down to the corpus callosum
must be cut away, and a hole cut through the corpus callosum.

2l6

ELEMENTS OF MAMMALIAN ANATOMY

A number of cross-sections of the cerebral hemispheres should
also be studied.

Each ventricle is composed of a body from which projects
an anterior cornu and a middle or descending cornu. The
former extends into the frontal lobe and thence into the olfac-
tory lobe, and the latter descends into the temporal lobe. The

Fig. io6. — Sagittal Section of the Brain.

ac. Anterior commissure; av, arbor vitce; c, habena; cc, canalis centralis; cb,
cerebellum; cm, middle commissure or massa intermedia; cr, sulcus crucialis;
cpq, corpus quadrigemina; ex, choroid plexus of third ventricle — the dark line
dorsad of ex is the velum interpositum; /, sulcus splenialis; /r, frontal lobe of
cerebrum; /w, anterior pillars of the fornix; in, infundibulum; it, iter, or aqueduct
of cerebrum; k, genu of corpus callosum; bnx, lamina terminalis; m, splenium; ma,
corpus niamillare; mr, sulcus marginalis; med, medulla; op, optic chiasm; oe,
occipital lobe; ol, olfactory lobe; pn, pineal gland; po, pons Varolii; pe, posterior
commissure; pv, inferior medullary velum; pvv, superior medullary velum or valve
of Vieussens; 3 and 4, third and fourth ventricles.

roof of the body of the lateral ventricle is formed by the cor-
pus callosum (Figs. io6, 107 and 108) and the medial wall by
the septum pellucidum, a mass of gray matter lying between the
fornix and the corpus callosum. A fringe of pia mater pro-
jects through the interventricular foramen of Monro into the
lateral ventricle, where it forms the choroid plexus. The
lateral ventricles are lined with the epithelial layer common
to the other ventricles.

THE NERVOUS SYSTEM 217

These cavities within the central nervous system result from
the manner in which the brain and cord are formed. In the
embryonic Ufe of most vertebrates the nervous system appears
as a trough of matter extending dorsally throughout the length
of the body. The sides of this trough grow dorso-mediad,
thus forming a roof and thereby converting the trough into
a canal which in the spinal cord becomes the canalis centralis,
and in the brain the ventricles. This continuous cavity of the
central nervous system contains a fluid having the nature of
the aqueous humor of the eye.

The Commissures of the Brain. — The paired portions of
the brain a e united across the median line by bands of fibers
known as commissures, two of which are visible on the ventral
surface of the brain, and the others may be seen in a sagittal
section (Fig. io6).

The pons Varolii is the commissure on the ventral aspect of
the medulla. Its fibers pass into the cerebellum on either side,
forming the middle peduncle or crus cerebelli ad pontem. The
optic commissure or optic chiasm is formed by the crossing of
the optic nerves, craniad of the tuber cinereum. Some of the
fibers originating in the cells of the retina of one eye pass by
this commissure directly to the cells in the retina of the other
eye, while a second set passes from the eye to the optic tract
on the opposite side of the brain, and still a third set, originat-
ing in one corpus quadrigeminum, passes by the optic commis-
sure direct to the opposite corpus quadrigeminum (Fig. 106).

The corpus callosum is the largest commissure of the brain.
It joins the two cerebral hemispheres, and forms the roof of
the lateral ventricles. This broad plate of fibers (Figs. io6,
107, 108, 109), which may be seen at the bottom of the great
longitudinal fissure by pressing the hemispheres slightly apart,
is about one millimeter thick and three centimeters wide.
Laterally the fibers radiate in all directions to the gray matter
of the cortex. The ventral bend of the median cranial portion
of the callosum is the genu or knee. The caudal border is
the splenium.

2l8

ELEMENTS OF MAMMALIAN ANATOMY

The foruix lies ventral to the callosum (Figs. io6 and io8) and
consists of a median plate of fibers, the body, two posterior
columns or crura, and two anterior columns. The median plate
or body of the fornix sends some fibers into the ventral surface

Fig. 107. — Dorsal Aspect of the Brain with the Cerebellum and the
Dorsal Third of the Cerebrum Removed and Most of the Corpus Callo-
sum Cut Away froxM the Right Half.

ac. Right anterior corpus quadrigeminum ; c, commissure of the quadrigemina;
ca, the united superior and inferior peduncles of the cerebellum; cr, the middle
peduncle of the cerebellum; cs, corpus striatum; ct, edge of corpus callosum cut
slightly to the left of the median line; cal, dorsal surface of the callosum into
which a hole has been cut; hp, hippocampus in the median cornu of the lateral
ventricle; h, hippocampus near where it is joined by the fibers of the crus of
the fornix; i, uncut portion of the callosum; md, medulla oblongata; n, columns
of the fornix; o, gray cortex of the cerebrum; p, crus of the fornix; pn, pineal
body, craniad to which is the heavy white line, the commissure of the habenae
or teniae thalami; pp, funiculus gracilis; re, funiculus cuneatus lateralis of Rolando;
/, funiculus cuneatus; ts, posterior corpora quadrigemina; x, body of the fornix.

of the callosum. From the cranial border of the body near the
median line the two anterior columns descend in a curve,
forming the cranial boundary of the third ventricle as far
ventrad as the anterior commissure. Here the two columns
diverge slightly from the median line, but continue their
descent, curving caudad to their termination in the corpora

THE NERVOUS SYSTEM 219

mamillaria. The posterior columns, or crura, descend from
the caudal border of the body, curving laterad into the median
cornu of the lateral ventricle, and gradually unite with the
hippocampus. The hippocampus is a thickened projecting fold
of the wall of the median cornu of the lateral ventricle (Fig.
107). The free lateral margin of the crus of the fornix is the
fimbria, or tcenia hippocampi. Adjacent to the median line
in either hemisphere, a thick lamina of matter, the septum
pellucidum, stretches from the cranial part of the fornix dorsad
to the callosum. The very narrow cavity formed by the ad-
herence of the margins of the septum of one hemisphere to
those of the septum in the other hemisphere is sometimes
called the fifth ventricle, or cavity of septum pellucidum.
Between each column of the fornix and the optic thalamus is
a cleft, the interventricular foramen leading from the third ven-
tricle, laterad of the septum pellucidum, into the lateral
ventricle.

The three remaining commissures are known according to
their location as the anterior, middle, and posterior. The ante-
rior commissure (Figs. 106 and 109) perforates the corpora
striata, extending across the median line immediately craniad
of the columns of the fornix. It is about two millimeters in
diameter. The middle commissure, or massa intermedia, lies
between the thalami. It is sometimes called the soft or gray
commissure. It is nearly one centimeter in diameter and passes
through the third ventricle (Fig. 106). The posterior commis-
sure is a cord of fibers about a millimeter in diameter connect-
ing the caudal portions of the thalami.

The Basal Ganglia. — A semi-independent group of nerve cells
forming a definite mass is known as a ganglion. In the ven-
tral portion of the brain lie three pairs of large ganglia, called
corpora quadrigemina, thalami, and corpora striata. To study
them, the entire dorsal surface of the brain down to and includ-
ing the corpus callosum should be removed.

2 20

ELEMENTS OF MAMMALIAN ANATOMY

The corpora quadrigcmina (Fig. 107) forming the dorsal part
of the mesencephalon lie craniad of the medulla, and consist
of an anterior pair and a posterior pair. The former are known
as the superior coUicidi and the latter as inferior colIicuH. The
anterior pair lie nearer to the midline than the posterior pair,
which are slightly separated by a depression occupied by the
middle portion of the central lobe of the cerebellum. The
posterior pair are united by a white commissure. The pos-
terior commissure of the brain unites the cranial portions of

Fig. 108. — Cross-section of the Brain in the Plane x in Fig. 105.
The plane is just caudad of the optic chiasm.
I and 2, First and second or lateral ventricles: cr, corpus callosum; cm, columns
of fornix; ex, choroid plexus of lateral ventricle; ex', choroid plexus of third ven-
tricle; cxt, gray cortex; ea, ependyma lining the ventricles;/, median longitudi-
nal fissure; h, taenia thalami; me, middle commissure, or massa intermedia;
n, fibers of the optic tract as they enter the lateral geniculate body s; o, fornix;
r, caudal portion of nucleus lenticularis; op, thalamus; oc, optic tract as it leaves
the chiasm; si, septum pellucidum; vn, part of third ventricle dorsad to the
commissure; v, third ventricle; /, fibers of optic tract.

the anterior pair (Fig. 106). Its cut end may be seen ventrad
to the base of the pineal gland.

Laterally each of the corpora quadrigcmina is prolonged
into two white bands, the anterior and posterior hrachia. The
latter are about a half centimeter long, and pass forward beneath
a pisiform ganglion, the corpus geniculattim internum or mediate.
The anterior brachia pass from the cranial end of the posterior
pair laterad beneath the caudal projections of the thalami,
where they join the optic tracts.

THE NERVOUS SYSTEM 221

Homologues of the corpora quadrigemina exist in all verte-
brates. In these bodies originate partly the optig nerves, and
therefore their size is in proportion to the animal's power of
sight. In the mole, which has little use for eyes, the anterior
pair is rudimentary.

The IhaJami forming the sides of the diencephalon or tween
brain are the largest pair of basal ganglia, and lie craniad of the
corpora quadrigemina and form the lateral walls of the third
ventricle, across which they meet, forming the massa intermedia;
or middle commissure.

On the dorsal aspect of each thalamus, near the median line,
is a longitudinal band of white fibers called the tcEuia ihalami,
which at its caudal limit is united to its fellow by the commis-
sure habenge. The thalamus is composed largely of gray matter,
but there are two important bundles of fibers, known as the optic
tract and internal capsule (Fig. io8), appearing on its lateral sur-
face. The optic tract, of which the optic nerve is a continuation,
arises by two roots, the larger of which comes from the cells
forming the lateral geniculate body, which is the lateral and cau-
dal projection of the thalamus. The internal capsule, well
shown in a transverse section, is composed of the fibers forming
a communication between the cells of the cortex and those in
the lower brain centers and spinal cord.

The pineal gland, or pineal body (Fig. io6), is a conical projec-
tion about a half centimeter long, from the caudal part of the
dorsal surface of the thalamus. It is a vestigial structure
which in some of the lower vertebrates in early geological time
functioned as a third eye. In Hatteria, a New Zealand lizard
about a foot long, the eye is present, projecting slightly through
a foramen in the parietal bone. Traces of this third eye with a
lens have also been noticed in the embryo of the viper and some
of the lizards.

The corpora striata lie deep in the telencephalon. They are
the most anterior of the basal ganglia and are somewhat pear-
shaped, the larger ends being craniad and nearer the median

222

ELEMENTS OF MAMMALIAN ANATOMY

line than the caudal })ortions, which curve laterad around the
optic thalami (Fig. 107). They form a part of the floor of the
lateral ventricles, and are pierced by the anterior commissure
(Fig. 109), a small cord of white fibers.

The corpus striatum consists of both white and gray matter.
The latter,' composed of cells, is disposed in two chief nuclei or
masses, known as the nucleus caiidatus, lying anterior and nearer
the median line than the nucleus lenticularis, which is more lateral

Fig. 109. — Cross-section of the Brain through the Anterior Commissure.
an. Arachnoid; ce, external capsule; cl, corpus callosum; cm, anterior com-
missure; jxc, falx cerebri; /, great longitudinal fissure; fx, columns of the fornix;
iCy internal capsule; «, radiating fibers of callosum; in, septum pellucidum; nc,
nucleus caudatus of corpus striatum; I, nucleus lenticularis; p, pia mater; vis,
superior longitudinal sinus; vn, third ventricle; v, lateral ventricle.

and caudal (Fig. 109). The center of the nucleus lenticularis is
laterad of the optic thalamus and dorsad of the crus cerebri. A
thin layer of white matter, the lamina semicircularis, separates
the optic thalamus from the nucleus caudatus. A few fibers
from the cerebral peduncles form the lamina semicircularis,
whose edge may be seen in the floor of the lateral ventricle on
the lateral boundary of the nucleus caudatus. A group of fibers,
known as the internal capsule, separates the thalamus from the
nucleus lenticularis, laterad of which is the external capsule, a
group of fibers probably descending from the cells of the cerebral
cortex. The two nuclei of the corpus striatum are connected
by fibers, and other fibers connect these nuclei w^ith the cortex
of the cerebrum and the optic thalamus.

THE NERVOUS SYSTEM 223

The Medulla Oblongata. — The medulla oblongata, or myel-
encephalon, is the stem of the true brain and extends from
the point of origin of the first spinal nerve to the pons Varolii.
The cerebellum must be removed in order to study carefully the
features of the medulla, and as it -is cut away the student should
notice just ventrad to it the very thin roof of the fourth ven-
tricle. Its caudal portion, composed of a reflection of the pia
mater lined with epithelium, takes the name of inferior medul-
lary velmn, and the cranial part, formed of pia and a thin layer
of nervous matter, is called the anterior medullary velum
(Fig. 106).

The fourth ventricle (Figs. 106 and 107) is an enlargement of the
canalis centralis of the cord. Two bands of fibers called clavce,
the three peduncles or crura of the cerebellum, and the posterior
corpora quadrigemina form its lateral boundaries. Its cavity is
shallow and pointed at either extremity. The floor, colled fossa
rhomboidea, is formed by the continuation of the gray matter
of the spinal cord. Where the ventricle is widest a tract of
fibers, the stria medullaris, arises from the midline and proceeds
laterad to help form the auditory nerve.

Laterad of the clava a larger band of fibers, the funiculus
cuneatus, runs parallel with a more lateral lying bundle, the
funiculus cuneatus lateralis, or funiculus of Rolando. The band
of fibers on either side uniting the cerebellum to the medulla
oblongata is the restiform body, or inferior peduncle of the cere-
bellum. On the ventral aspect of the medulla may be seen the
anterior pyramids, composed of a band of fibers lying on either
side of the median line and apparently emerging from the pons.
They form a section of the crossed pyramidal or motor tract
connecting the brain with the cord. The olivary eminence lies
just laterad of the pyramid. The fact that seven posterior
cranial nerves originate from the medulla shows the importance
of this part of the brain. The destruction of the respiratory
centers, or vital knot, lying ventrad to the caudal end of the
fourth ventricle causes instant death.

224 ELEMENTS OF MAMMALIAN ANATOMY

The Cerebellum, or Little Brain.— The cerebellum, which in
the cat lies caudad of the cerebrum and dorsad of the medulla,
resembles the cerebrum in being composed of an outer layer of
gray matter or cells and an inner mass of white matter made up
of fibers. While within the cerebrum there are several impor-
tant ganglia or masses of gray matter, in the cerebellum only
one chief mass of gray matter, the corpus dcnlatum, is present
in each hemisphere.

The outer layer of gray matter, known as the cortex, is folded
into numerous convolutions, between which are deep sulci
(Fig. io6). The central core of white matter forms an arbor-
escence known as the arbor vitce.

The cerebellum (Fig. 103) is seen to consist externally of two
lateral portions, the cerebellar hemispheres, a median vermiform
process and three pairs of peduncles or crura which are bands
of fibers uniting it with other parts of the brain and cord
(Fig. 107) . The separation between the hemispheres and vermis
or vermiform process is most marked on the cranial aspect.

The peduncles are named, according to their location, supe-
rior, middle, and inferior. The middle peduncle, or brachium
pontis, is a dorsal prolongation of the fibers of the pons Varolii
(Fig. 104). In order to display the other peduncles a portion of
the cerebellum must be cut or picked away with the forceps.
The superior one, known also as the brachium conjunctivum, ex-
tends as a cord of fibers along the cranial half of the fourth
ventricle and then beneath the corpus quadrigeminum. The
inferior peduncle, or restiform body, forms part of the boundary
of the caudal half of the fourth ventricle and enters the cere-
bellum between the other two peduncles. It is composed of
fibers from the spinal cord and medulla.

LABORATORY STUDIES AND SUGGESTIONS

1. Describe the meninges of the central nervous system.

2. Which of the five parts of the brain are exposed dorsally?

3. Draw the lateral aspect of the brain and label all features.

4. Draw the ventral aspect of the brain and label all features.

5. Draw the dorsal aspect of the brain after the dorsal portion, including
corpus callosum and fornix, has been removed.

THE NERVOUS SYSTEM 225

6. Describe the differences existing between the gyri and sulci of your
specimen and the one described in the text.

7. Write a description of the ventricles, giving dimensions and boundaries.

8. Describe the attachment of the pineal body.

9. Which of the cranial nerves derive their name from their function?

10. Name the foramina giving passage to one or more of the cranial nerves.

11. From which of the five parts of the brain do most of the cranial nerves
originate?

12. Describe the choroid plexus.

13. What is the internal capsule?

14. Draw a cross-section of the brain made by cutting through the optic
commissure and label all parts.

15. Draw a cross-section of the brain made by cutting through the middle
commissure and label all parts.

16. Draw a cross-section of the brain made by cutting through the corpora
qudrigemina and label all parts.

17. Write a description of the corpus callosum.

18. Which is the smallest commissure of the brain?

19. Explain the difference in structure between the white and gray matter.

20. Describe the cerebellum.

THE SPINAL CORD

The spinal cord extends from the foramen magnum through
the vertebral canal. It is more or less cylindrical throughout
and has a diameter of about one centimeter except in the
lumbosacral region, where it grows gradually smaller until it
is only one or two millimeters in diameter. In order to study
the cord, one should have a mounted transverse microscopic
section, and an entire cord in situ with the dorsal wall of the
vertebral canal removed, so that the exit of the spinal nerves
may be seen.

The membranes (Fig. no) which envelop the spinal cord

are the same as those that envelop the brain. The dura mater

is the external tough coat; the pia mater, the internal delicate

vascular coat sending a process deep into the anterior fissure

on the ventral side; and the arachnoid, the very thin membrane

between the two preceding. The arachnoid lies close against

the dura mater, but is separated from the pia mater by the

subarachnoid space, which is filled with a serous fluid called

the cerebrospinal fluid. It is apparently the same as that in
15

226

ELEMENTS OF MAMMALIAN ANATOMY

the ventricles of the brain and the aqueous humor of the eye.
It seems to be supplied for the most part by the choroid plexus
of the ventricles although other sources have been suggested.
The cord presents two enlargements, the cervical, whence
issue the nerves of the forelimbs, and the lumbar, giving origin

Fig. 1 10. — Photomicrograph of Cross-section of Human Spinal Cord.

a, Arachnoid membrane; an, ventral side in which appears the deep anterior
fissure; d, dura mater; n, one of several nerve bundles; the tiny white spot in the
center of the dark gray matter is the canalis centralis; p, pia mater. X 5.

to the nerves of the posterior limbs. Two deep fissures, the
ventral (anterior) median and the dorsal (posterior) median,
penetrate about one-third through the cord, incompletely divid-
ing it into halves longitudinally. The pia mater is prolonged
into the ventral fissure, but not into the dorsal fissure. Slightly
laterad of the ventral median fissure issue the ventral roots
of the spinal nerves, and at about the same distance from the
dorsal median fissure are the dorsal roots of the spinal nerves.
These two roots unite about one centimeter from their origin

THE NERVOUS SYSTEM

227

(Fig. 104). On the dorsal or sensory root is a small ganglion
located very near the junction of the two roots. The common
spinal nerve, formed by the union of the two roots, almost
immediately divides into four branches, one of which, the dor-
sal, supplies the muscles and skin along the vertebral column;
a second, the ventral branch, supplies the limbs or intercostal
spaces; while the other two branches, rami communicantes ,
join the adjacent ganglion of the sympathetic cord (Fig. 118).

Fig. III. — Diagrammatic Cross-section of the Spinal Cord. The cells
and fibers are represented too few and too large in proportion to the size of the
cord.

ag, Ventral horn or column of gray matter; a, nerve process of the cell; c,
an, ventral root; cc, central canal; c, one of the cells forming the ganglion
on the dorsal root; d, dorsal median sulcus; e, cell giving off an axone into
the ventral root; dn, dorsal branch;/, cut-off fibers; gti, ganglion of dorsal root;
i, axone of the cell io; «c, junction of dorsal and ventral roots; /j^, dorsal root
of nerve; pg, dorsal column of gray matter; s, terminal arborization of part of
fiber from c; v, ventral median fissure; vn, ventral branch of nerve; van, axones
of ventral column cells; x, the part of the dorsal root fiber extending craniad in
the cord.

Each of the four branches contains both motor and sensory
fibers, or, in other words, fibers from both roots.

The exit and entrance of the nerve roots divide the w^hite
matter of the lateral half into three columns named, according
to their location, the ventral column, the lateral column, and the
dorsal column. The first is ventral to the ventral nerve roots,
the last is dorsal to the dorsal nerve roots, while the lateral
column is between the roots.

228

ELEMENTS OF MAMMALIAN ANATOMY

The elements of the spinal cord, like those of the brain, are
of two kinds — the cells composing the gray matter and the
fibers composing the white matter. While in the brain the
gray matter is largely on the surface, forming the cortex, in
the cord it occupies the central region. A canal, the canalis
cciilralis, about one-half a millimeter in diameter, extends
throughout the cord, opening into the fourth ventricle of the

Fig. 112. — Cell from the Central Nervous System. X loo.
a, Dendrites or protoplasmic processes; ax, axone; n, nucleus of the cell body.

brain. A cross-section of the cord shows the gray matter
arranged in the shape of a letter H. The ventral columns of
gray matter are the ventral horns, and the posterior columns,
the dorsal horns (Fig. in).

Many of the fibers extend in a longitudinal direction through-
out the cord, but the roots of the spinal nerves upon entering
the cord run transversely a longer or shorter distance, and in
many cases cross to the opposite side. Numerous experiments

THE NERVOUS SYSTEM

229

c^r^^

I t 4-....

IT2

I I I

Fig. 1 13. — Diagram Showing the Relation of Some of the Cells and Fibers
OF the Spinal Cord. Lateral aspect of the cord.
a. Ventral median fissure; ac, cells of the ventral horn; ayi, ventral root of
spinal nerve; c, axone; co, collateral fibers; e, fibers connecting higher brain
centers with cerebellum;^, sensory fibers of fillet to the brain; g, gn, go, ganglion
of dorsal root; gr, gray matter; ir, fibers of the dorsal sensory tract; I, fibers to
cerebellum; m, cell in the ventral horn or column of gray matter; n, spinal nerves;
o, cells in the dorsal horn or column of gray matter; nc, nucleus gracilis and
nucleus cuneatus; nr, nucleus ruber; r, a fiber of posterior root; rb, ganglion
cells of medulla; s, tract of fillet to the brain; sp, fibers of superior peduncle of
the cerebellum; /', fiber of crossed pyramidal tract; ts, point of decussation; v,
division of fiber x into its cranial and caudal extensions; w, a collateral of the
longitudinal fiber ir.

230 ELEMENTS OF MAMMALIAN ANATOMY

show that the ventral root fibers are, for the most part, the
axones of the cells in the ventral horn (Fig. 113).

Each dorsal root fiber after passing into the cord separates
into two parts one of which extends craniad, the other caudad
(Fig. 113). Both give off branches at right angles, called
collaterals, which terminate in arborizations about the cells
of the cord.

Each nerve cell with all its processes is called a neurone. It
presents two kinds of processes, protoplasmic processes or den-
drites and an axis-cylinder process or axone (Fig. 112). The
dendrites, except in the gangha outside of the central nervous
system, are usually several in number and comparatively short,
while there is but one axone from each cell, which may be more
than a foot in length. A number of axones (nerve fibers),
each of which is surrounded by a sheath, the neurilemma,
constitutes a nerve bundle or nerve. Every axone or nerve
fiber originates in a cell, but terminates freely either within
the central nervous system or in some other part of the body
(Figs. 112, 113). Within the central nervous system a fiber
usually ends in an arborescence which may be contiguous but
not continuous with the dendrites of another cell. The nerve
processes have the power of conducting impulses whether
derived from the cell itself or an external stimulus. The den-
drites conduct impulses toward the cell, while the axone con-
ducts them from the cell.

The sensory fiber r (Fig. 113), leads from the dermis of the
cat's paw. A pin-prick in the paw causes an impulse to be
transmitted along the fiber to the cell g, and thence by its
axone, x, to the point v within the cord where the fiber splits.
From the point v the impulse will proceed both through the
ascending portion of the fiber, ir, and the collateral, w. By
the latter route it will stimulate the cell w, whose axone termi-
nates in the foreleg muscles, which are thereby made to con-
tract and pull the paw away from the irritating object. This
process may take place without consciousness, and is then

THE NERVOUS SYSTEM 23 1

known as reflex action. If, however, the impulse travels along
the fiber ir, and thence through the fiber s to the brain, whence
an impulse descends through the fiber t' , ts, the process is known
as voluntary reaction.

LABORATORY STUDIES AND SUGGESTIONS

1. Describe the membranes of the cord.

2. What diflference is there in the size of the nerve roots in the various regions
of the cord?

3. Draw a cross-section of the cord showing all features visible to the naked
eye.

4. How does the arrangement of the gray matter of the cord and brain dififer?

5. Describe the processes of nerve cells.

6. In what portions of the body are nerve cells found?

7. Procure a piece of spinal cord from the butcher-shop. Smear a bit of the
gray matter on a glass slip, dry, then stain in hematoxylin, wash, and after
drying mount in balsam. Draw and describe nerve cells thus found.

THE PERIPHERAL NERVES

All portions of the head, trunk, and limbs of the cat are
supplied with nerve fibers which are in communication with
the central nervous system by means of fifty-two pairs of
nerve bundles, forming what are known in the brain region as
the cranial nerves and in the region of the cord as the spinal
nerves.

The Cranial Nerves. — There are twelve pairs of cranial
nerves, all of which pass through foramina in the base of the
skull, and all except one, the tenth or vagus, are distributed
to structures of the head and neck.. They are divided accord-
ing to function into motor and sensory. Some of the nerves
communicate with the brain by more than one root, and in
such cases the same nerve may have sensory fibers in one root
and motor fibers in another. For example, the trigeminal
nerve transmits a stimulus causing the muscles of mastication
to contract and also supplies the teeth and other portions of
the fore-parts of the head with sensory fibers (Fig. 104).

The olfactory (I), optic (II), and acoustic (VIII) are the only
cranial nerves wholly sensory. The oculomotor (III), troch-

232

ELEMENTS OF MAMMALIAN ANATOMY

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THE NERVOUS SYSTEM 233

learis (IV), and ahducens (VI) are wholly motor. The tri-
geminal (V), facial (VII), glossopharyngeal (IX), Vagus (X),
accessorius (XI) (mainly motor), and hypoglossus (XII) contain
both motor and sensory fibers.

The dissection of the cranial nerves is very difficult. A head,
containing a brain hardened by a formalin injection, should
be placed in 500 c.c. of 5 per cent, nitric acid, which will decal-
cify the bone in about a week. After washing out the acid by
soaking the specimen in running water twenty-four hours, the
dissector may with much care follow the nerves peripherad from
their origin at the base of the brain. The vagus nerve must,
of course, be traced in an entire specimen, where it may be
easily followed in the neck region along with the carotid artery,
whence it passes to the lungs and stomach (Fig. 72).

Some of the sensory nerve roots bear ganglia, the largest
of which is the semilunar (Gasserian) ganglia, more than a half
centimeter in diameter, forming a knot on the sensory root of
the trigeminal, within the cranial cavity (Fig. 104).

The Spinal Nerves. — There are forty pairs of nerves connected
with the spinal cord. They issue from the vertebral canal
through the intervertebral foramina. Each nerve is connected
to the cord by a ventral and dorsal root (Figs. 104 and 113). The
former is also known as the motor root, since its fibers are almost
entirely motor, while the latter is the sensory root, as it is com-
posed of fibers transmitting impulses to the central nervous
system. A ganglion about the size of a pinhead is located on
the dorsal root immediately proximad of its junction with the
ventral root, within the intervertebral foramen. This anatomy
can be displayed by cutting away the dorsal muscles on either
side of the column, and then, with the bone-cutters, severing
the laminai of several of the arches of the vertebra?, so that
the roof may be removed from the vertebral canal (Fig. 23).

Immediately beyond the intervertebral foramen each nerve
gives off a dorsal branch to the muscles of the back, and a small
connecting twig to the sympathetic system. The main nerve

234

ELEMENTS OF MAMMALIAN ANATOMY

is then spoken of as the ventral branch. These main nerves or
ventral branches, in various regions of the trunk, anastomose

Fig. 114. — Ventral Aspect of the Brachial Plexus and Chief Nerves of

THE Arm.
6, 7. 8 and i, Sixth, seventh, and eighth cervical and first dorsal nerves; at, alh,
anterior thoracic nerves; a and b, to muscles of the forearm; c and d, to the joint;
ex, circumflex nerve; cu, internal cutaneous; de, to the deltoid; g, to the digits;
/, to the digits; fo, supracondyloid foramen; //, long thoracic; mc, musculo-
cutaneous; me, median nerve; pi, posterior interosseous; pth, posterior thoracic;
sp, musculospiral; sp, to suprascapular region; sb, to subscapular region; sx,
subscapular; ra, radial; un, ulnar nerve.

with each other, forming plexuses. In the region of the neck,
where is formed the cervical plexus; in the region of the shoulder
the brachial plexus; in the region of the loins, the lumbar plexus;

THE NERVOUS SYSTEM 235

and in the region of the sacrum, the sacral plexus (Figs. 114 and

IIS).
There are eight cervical nerves, the first of which does not

make its exit through the intervertebral foramen, as do all the
other spinal nerves, but traverses a foramen in the atlas. The
first five cervical nerves, the three posterior cranial nerves, and
branches from the sympathetic trunk, form the cervical plexus.
These five cervical nerves supply mainly the structures of the
neck.

There are thirteen pairs of thoracic nerves. The ventral
branches of the sixth, seventh, and eighth cervical nerves and
the first thoracic nerve form the brachial plexus. This may be
displayed by remo\ing the cephalo-humeral muscle and cutting
through the pectoral muscles about two centimeters from their
origin (Fig. 48) . The manner in which the nerves anastomose
varies somewhat, but the following will be found approximately
correct :

The sixth cervical nerve gives off a small branch to the rhom-
boideus and levator scapulae muscles of the shoulder, and then
divides into two nearly equal branches, one of which supplies
the muscles on the lateral aspect of the scapula, and the other
joins with the seventh cervical nerve. Small branches from
the fifth and sixth cervical nerves unite to form the phrenic
nerve supplying the diaphragm.

The seventh cervical nerve gives off three small branches at
about the same point, one of which is the posterior thoracic
supplying the serratus magnus muscle, a second helps to form
the musculocutaneous, and the third forms part of the median
and anterior thoracic. The main portion of the seventh cer-
vical unites with the eighth and first thoracic, to form the mus-
culospiral (radial) nerve. The circumflex (axillaris) and sub-
scapular branches supplying the deltoid and subscapular muscles
are also derived from the seventh.

The eighth cervical nerve, after giving off a small branch to the
pectoral muscle, a small twig to the median nerve, and a large

236 ELEMENTS OF MAMMALIAN ANATOMY

branch to the first thoracic nerve, is continued as the main part
of the muscuh)spiral nerve.

The first thoracic nerve gives first a large branch to the mus-
culospiral nerve, a second small branch to the anterior thoracic,
and a third branch forming the internal cutaneous nerve supply-
ing the skin of the arm and forearm on the caudal aspect. The
main portion of the first thoracic nerve then continues as the
main part of the ulnar nerve.

The nerves of the forelimb are five in number (Fig. 114) : the
external cutaneous or musculo-cutaneous, the internal cuta-
neous, the musculospiral, the median, and the ulnar. The
external cutaneous arises from the sixth and seventh cervical
nerves and passes distad along the caudal aspect to the biceps
to the cranial aspect of the forearm, where it becomes subcutane-
ous. It supplies the biceps and coracoid muscles and the skin
of the forearm. The internal cutaneous arises from the first
thoracic and passes along the ventral side of the arm, becoming
subcutaneous just proximad of the elbow, where it is distributed
to the skin of the arm and forearm on the cadual and ventral
aspects.

The musculospiral (radialis) arises from the seventh and
eighth cervical and first thoracic nerves. It is the largest
component of the brachial plexus. It winds obliquely around
the humerus to the cranial aspect, where it divides into two
branches, the radial and the posterior interosseous. The
superficial radial nerve is the smaller and becomes subcutaneous
near the elbow, and passes along the radial region. The
posterior (dorsal) interosseous proceeds along the dorsal aspect
of the forearm to the wrist, where it divides into branches
supplying the digits.

The median nerve arises from the seventh and eighth cervical
and first thoracic. It follows the course of the brachial artery,
passing through the supracondylar forearm to the elbow, where
it passes beneath the pronator teres to the carpal region, and
supplies the first, second, and third digits. It also supplies the
pronator teres and flexor muscles of the forearm.

THE NERVOUS SYSTEM 237

The ulnar nerve (Fig. 114) is derived from the eighth cervical
and first thoracic. It courses with the brachial artery to the
middle of the humerus, where it turns caudad to pass between
the olecranon process and internal condyle of the humerus. It
is here subcutaneous and furnishes the sensation experienced
when one strikes what is popularly called his ''funny bone," but
what is really the ulnar nerve. It then passes down the ulnar
side of the forearm, supplying some of the flexor muscles, and
finally divides to supply the fourth and fifth digits. The ven-
tral branches of the remaining thoracic nerves encircle the body,
supplying the muscles and skin of those regions.

The lumbar plexus (Fig. 115) is composed of the anastomos-
ing of the ventral branches of the four caudal lumbar nerves.
As in the cervical and thoracic nerves, the lumbar nerves divide
into dorsal and ventral branches immediately without the inter-
vertebral foramen. The former supply the muscles and skin of
the back. In order to display the lumbar nerves, the entire
ventral and lateral abdominal wall should be cut away and
the specimen securely nailed to the tray on its back. The
adipose tissue and muscles lying on either side of the bodies of
the lumbar vertebrae must be carefully picked away until the
roots of the nerves are apparent. They may then be easily
followed distad.

The first three lumbar nerves of the cat are represented in
man by the ilio-hypogastric and ilio-inguinal. The first nerve
supplies the rectus muscle and skin of the abdomen. This
nerve and the two next described are scarcely as large in diam-
eter as an ordinary pin. The ventral branch of the second lum-
bar nerve divides into two branches, and supplies the skin of the
caudal part of the abdomen, and structures in the inguinal
region. The ventral branch of the third lumbar nerve supplies
the inguinal region and is also distributed to the transverse and
rectus muscles. The fourth lumbar nerve divides into two
parts, one of which is the genito-crural (genitofemoral) nerve,
supplying the skin and other structures of the ventral abdominal
wall and thigh, the other branch together with part of the fifth

238

ELEMENTS OF MAMMALIAN ANATOMY

Fig. 115. — Ventral Aspect of the Nerves of Hind-limb.

4, 5, 6, 7, I, 2, and 3, Fourth, fifth, sixth, and seventh lumbar, and first,
second, and third sacral nerves; a, branch from the fourth to the fifth; ac, an-
terior crural; cu, saphenous; d, anterior tibial; e, peroneal or musculocutaneous;
ex, external popliteal or peroneal; ef, external plantar; /o, obturator foramen;
gs, greater sciatic; g, genito-crural; H, internal popliteal; ip, internal plantar;
kn, knee; /, external cutaneous; Is, lumbosacral cord; t, posterior tibial; s, small
sciatic.

THE NERVOUS SYSTEM 239

nerve forms the external cutaneous, supplying the lateral surface
of the thigh region.

The anterior crural nerve is composed mainly of branches of
the fifth and sixth lumbar. It receives a small branch from the
fourth. It supplies the psoas muscles, which it pierces, and
then divides into several branches, one of which is the saphenous,
passing subcutaneously along the medial aspect of the leg. The
other nerves supply the muscles of the thigh on the cranial and
medial aspect. The obturator nerve is composed of branches
from the sixth and seventh lumbar. It is smaller than the pre-
ceding, and passes through the obturator foramen to supply the
obturator, adductor, gracilis and pectineus muscles.

The sacral plexus is formed of the three sacral nerves with
branches from the sixth and seventh lumbar nerves.

The great sciatic nerve is composed mainly of the ventral
branches of the seventh lumbar and first sacral nerves. It usu-
ally receives accessions from the other sacral nerves and the sixth
lumbar. The great sciatic is the largest peripheral nerve in the
body. It passes caudad from its origin around the greater
sciatic notch and thence along the caudal aspect of the thigh to
the popliteal space, where it divides into the internal and
external popliteal nerves. The former continues down the caudal
side of the tibia as the posterior tibial nerve to the internal mal-
leolus, where it divides into internal and external plantar nerves,
which supply the digits. The external popliteal or peroneal
nerve extends to the outer cranial aspect of the leg, where it
divides into the musculocutaneous and anterior tibial nerves.
The former extends between the extensor longus digitorum and
peronei muscles to its ramification on the dorsum of the foot.
It supplies the skin along its course and the peronei muscles.
The anterior tibial nerve passes down on the cranial aspect of
the tibia beneath the extensor longus digitorum muscle to the
tarsal region, where it anastomoses with a branch of the external
cutaneous, and supplies the skin, tibialis anticus, and the
extensor muscles.

240 ELEMENTS OF MAMMALIAN ANATOMY

The lesser sciatic nerve comes chiefly from the second and
third sacral nerves. It suppHes the region of the anus and the
biceps muscle.

Other nerves given off from the sacral plexus are the glutei
and pudic nerves supplying the buttock muscles and external
genital organs.

THE SYMPATHETIC NERVOUS SYSTEM

The sympathetic nervous system is composed chiefly of a pair
of nerve-cords extending from the base of the skull to the root of
the tail, a number of ganglia and branches supplying the thoracic
and abdominal viscera, and numerous minute libers supplying
the muscular walls of the blood-vessels in all parts of the body.
The sympathetic system supplies all non-striped or involuntary
muscles in any part of the body. The two branches connecting
each spinal nerve with a sympathetic nerve-cord are called rami
c 0 mm unic antes.

In order to demonstrate this system successfully, one should
use a lean injected specimen. After the cat has been securely
nailed on its back to the tray, the entire ventral half of the
thoracic and abdominal walls should be removed. By pushing
the heart and lungs to the left side a white cord about one milli-
meter in diameter may be seen lying near the median dorsal line
(Fig. 116). The left cord may be found in a similar manner and
both followed craniad and caudad, noting their numerous
branches in accordance with the following description.

The sympathetic nerve -cord begins in the superior cervical
ganglion lying near the angle of the mandible, beneath the sub-
maxillary and lymphatic glands. This ganglion is about the
shape of a grain of wheat, but not more than half so large, and
is adjacent to the small vagus' ganglion on the dorsal side of the
carotid artery. The ganglia are masses of large nerve cells and
occur at regular intervals on the sympathetic cords in the body
cavity, and are present also on some of the branches of the cords
(Fig. 117). On the cords there are three pairs of cervical ganglia,

THE NERVOUS SYSTEM

241

thirteen pairs of thoracic ganglia, seven pairs of lumbar ganglia,
and one or two pairs of sacral ganglia, in addition to two median
unpaired sacral ganglia.

In the cervical region the sympathetic and vagus, or tenth
cranial nerve, are bound in a
common sheath lying along the
lateral aspect of the carotid
artery. One or two centimeters
craniad of the first rib is the
thyroid or middle cervical gang-
lion, whence the nerve proceeds
in two cords, enclosing the sub-
clavian artery, to the large in-
ferior cervical ganglion just
caudad of the first rib. From
the cervical portions of the
sympathetic cord are given off
numerous delicate branches,
forming the carotid plexus on
the carotid artery, and uniting

Fig. 116. — Chief Part of Left Half
OF Sympathetic System Craniad of
THE Diaphragm. Semidiagrammatic.

5, 6, 7. 8, 9, and 10, Fifth, sixth,
seventh and eighth cervical nerves, and
first and second thoracic spinal nerves:
a, the dorsal branch of the left vagus
/n; an, dorsal branch of the right vagus;
ax, common dorsal vagus formed by a
and an; avb, ventral vagus; he, cardiac
branch of sg, cr; carotid plexus; car,
carotid artery; cm, rami communicantes;
cp, cardiac plexus; dia, diaphragm; g,
ganglia in the thoracic cavity; ig, mid-
dle cervical ganglion; Ig, portion of left
lung; In, left vagus nerve; nv, cranial
nerve; pn, phrenic nerve; pp, pulmo-
nary plexus; sn, sympathetic cord; sm,
superior cervical ganglion; sb, left sub-
clavian artery; sg, stellate ganglion or
inferior cervical; spin, splanchnic major
nerve; vg, vagus ganglion; v, vagus nerve.
16

242

ELEMENTS OF MAMMALIAN ANATOMY

with the eight posterior cranial nerves and the first spinal
nerve. From the inferior cervical ganglion a branch goes
to the vagus nerve,

several branches to the brachial

Fig. 117. — Chief Part of Left Half of Sympathetic System Caudad of the
Diaphragm. Semidiagrammatic.
bl. Bladder; ce, celiac axis; du, duodenum cut ofif; dia, diaphragm; gr, anterior
gastric plexus; g, ganglion; im, inferior mesenteric artery; il, external iliac artery;
7ig, dorsal branch of vagus (Fig. 106. ax) ; «/, ventral branch of vagus; oe, esopha-
gus cut off; p, superior mesenteric plexus; plx, inferior mesenteric plexus; px,
branches to dorsal gastric plexus; rn, renal plexus; s?n, superior mesenteric
artery; spn, splanchnic major or greater splanchnic nerve from the sympathetic
cord; sg, semilunar ganglion; spc, sympathetic cord of left side.

plexus, and a branch to the heart, forming the cardiac
plexus, while the main sympathetic cord continues along the
dorsal thoracic wall. A ganglion occurs opposite each verte-
bral body, from which it gives off a branch to the corresponding
spinal nerve. The great splanchnic arises from the main cord

THE NERVOUS SYSTEM 243

just craniad of the diaphragm and extends to a group of ganglia
in the region of the trunk of the celiac axis (Figs. ii6 and 117).
These ganglia and anastomosing branches constitute the solar
or epigastric plexus, lying dorsad of the stomach, to which it
sends numerous branches. This plexus also receives the lesser
splanchnic nerve coming from the sympathetic cord just
craniad of the diaphragm, and branches from the tenth cranial
nerve.

The largest ganglion of the solar plexus is the celiac or semi-
lunar. The solar and its allied plexuses send nerves to the dia-
phragm, suprarenal bodies, many of the blood-vessels of the
abdominal cavity, stomach, kidneys, ureters, testes or ovaries,
uterus, liver, gall-bladder, spleen, pancreas, and intestines.

The hypogastric plexus is the third great sympathetic plexus.
It lies on the ventral aspect of the two caudal lumbar vertebrae
and is formed by branches from the solar plexus and a few twigs
form the sympathetic cords. It supplies the blood-vessels of
the pelvic region and all the organs of the pelvis. The sym-
pathetic cords in the lumbar region lie near together and the
communicating branches between them and the spinal nerves
are longer than in the thoracic region. In the sacral region
there are no rami communicantes, and the ganglia are irregularly
arranged. A median ganglion in the sacraL region is known as
the ganglion impar. There may be two median ganglia. The
sympathetic cords terminate in the tail.

LABORATORY STUDIES AND SUGGESTIONS

1. Name the foramina of the skull giving passage to one or more cranial
nerves.

2. From a study of one or more specimens and the description in the book
make a diagrammatic drawing of each cranial nerve.

3. Which cranial nerves have their roots in the medulla?

4. Name the cranial nerves which are wholly motor.

5. Which of the cranial nerves do not supply structures of the head?

6. Of what are ganglia composed?

7. Make a drawing of your dissection showing the connection between the
spinal and sympathetic nerves.

244 ELEMENTS OF MAMMALIAN ANATOMY

8. Which spinal nerves form the several plexuses?

g. Make a ilrawing showinj; wherein the brachial plexus in your specimen
differs from that described in the text.

10. Write a description of your dissection of the nerves of the thoracic limb,

11. Mention in what way the lumbar plexus dilTers from the description
in the book.

12. Draw the great sciatic nerve and its branches as seen from the caudal
aspect.

13. What nerves supply the digits?

14. Describe the chief plexuses of the sympathetic system.

15. How do stimuli from the viscera reach the brain?

16. What portion of the body is not supplied with nerves from the sympa-
thetic system?

THE ORGANS OF SENSE

The organs of sense are the specialized peripheral termina-
tions of the sensory nerves, and are so constructed as to be
capable of receiving only a certain kind of stimulus. The
stimuli for the eye are ether vibrations; those for the ear are
vibrations of the air. The stimulation of the sensory nerves
produces sensations in the cells of the cerebral cortex to which
they lead.

The external stimuli giving rise to the internal sensations
of seeing, hearing, smelling, and tasting are transmitted by
only four pairs of cranial nerves, while the stimuli of cutaneous
sensations are transmitted by three pairs of cranial nerves
and all the spinal nerves.

Cutaneous Sense Organs. — The cutaneous sense organs are
composed of the endings of the sensory nerves in all parts of
the skin and the mucous membrane of the mouth, nose,
arms, vagina, and urethra. One kind of sense organs, those of
pain, are present in every organ of the body. The sense organ
of pain is probably an unmodified free nerve-ending.

While all portions of the skin and perhaps other parts of the
body are supplied with organs capable of receiving stimuli
giving rise to tactile sensation, the soles of the feet and the
skin at the base of the vibrissae are specially sensitive regions.

THE NERVOUS SYSTEM

245

The nerves terminate in a kind of wreath formation about
the base of the vibrissae.

All of these sense organs are invisible to the naked eye
except the Pacinian corpuscles. If the mesentery is held up
and looked through toward the light, the Pacinian corpuscles
or sensory nerve terminations appear as translucent oval bulbs
about two miUimeters long. If a piece of the mesentery con-
taining a corpuscle is pinned tense on a piece of cork and then
cut out and placed ten minutes in 3%
acetic acid, the termination of the nerve
wdthin the corpuscle may be seen with a
microscope magnifying thirty diameters.
All the spinal sensory nerve fibers enter
the cord by the dorsal root (Figs. 104 and
III).

The Olfactory Organ. — The organ of
smell lies in that part of the mucous

Fig.

membrane lining the caudal part of the corpusc

118. — Pacinian
:le from the

nasal cavity and the basal third of the Mesentery, x 20.

, , . 1 , /-r^. V rr^. OX, Axis-cylinder ; n,

ethmoturbmal bones (Fig. I9J. That neurilemma; m, the

part of the mucous membrane containing !?^f-^Y ^^J^^^^^' ^' ^^^"
the olfactory cells is known as the

Schneiderian membrane. In a fresh specimen it is of a grayish
color while the other mucous membrane is red. The first
pair of cranial nerves convey the olfactory impulse to the brain.
They pass through the foramina in the cribriform plate of the
ethmoid bone, to the olfactory bulbs, from each of which
two roots extend to the base of the cerebrum (Fig. 104).

The Gustatory Organ. — The organ of taste is located chiefly
in the mucous membrane on the dorsum of the tongue, the
soft palate, the pillars of the fauces, epiglottis, and part of
the cheek. On the dorsum of the tongue are seen four kinds of
papillae — the vallate, the fungiform, the filiform, and flat. The
vallate papillae are from eight to twelve in number, forming
two sides of a triangle on the caudal portion of the dorsum of

246 ELEMENTS OF MAMMALIAN ANATOMY

the tongue. The fungiform are l)lunt papillae scattered sparsely
in the midst of the numerous filiform or pointed papillae (Fig.
62). The special organs of taste, known a.s tasle-biids, are very
numerous in the fungiform and vallate papillae of most mammals,
but in the cat they are few and not well differentiated. These
taste-buds occur in many parts of the mucous membrane of the
mouth cavity, each being supplied with a branch of the glosso-
pharyngeal nerve.

The Visual Organ. — The special organ of sight is the eye,
which occupies the orbital cavity of the skull. The ball of
the eye is protected above and below by extensions of skin
called the eyelids or palpebrae, which are lined with mucous
membrane, a transparent layer of which, known as the con-
junctiva, extends over the front of the eyeball between the
two lids. The dorsal lid is raised by the levator palpebrae
muscle, which has its origin in the occipitofrontalis muscle.
A sphincter muscle, the orbicularis oculi (palpebrarum), lies on
the margin of the lids, and by its contraction closes the eye.

The point on either side where the two eyelids meet is
termed the canthus or angle. At the medial or inner canthus
are two minute apertures, the puncta lachrymalia, leading into
two short canals which unite to form the nasal duct. The
lachrymal canal, which forms the channel for this duct, is
clearly visible in the lachrymal bone of the dried skull. At
the medial canthus there is a prominent fold of mucous mem-
brane, the membrana nictitans, or plica semilunaris, which is
a rudimentary structure in the cat, but is found well developed
in birds which have the power of sweeping it rapidly across
the eyeball, thereby removing dust.

On the inner surface of each lid are the large sebaceous
tarsal glands. The lachrymal gland lies in the dorso-lateral
region of the orbit, and its ducts open on the ventral surface
of the upper lid, whence the tears flow over the conjunctiva
ventrad to the puncta lachrymalia. The Harderian gland is

THE NERVOUS SYSTEM

247

the very small mucus-secreting gland at the medial canthus.
It is usually vestigial or absent in man and other primates.
The muscles controlling the movements of the eyeball are
seven in number: four are recti muscles, two are oblique, and
one is a retractor. The recti muscles (Fig. 104) originate on
the bone around the optic foramen, and are inserted on the
sclerotic coat, caudad of the equatorial ring. The external
rectus is inserted on the lateral aspect; the internal rectus, on
the medial aspect; the superior rectus, on the dorsal aspect;
and the inferior rectus on the ventral aspect. The superior

Fig. 119. — Longitudinal Section of the Eye.
aq. Aqueous humor; c, cornea; cp, capsule of the lens; ch, choroid; ci, ciliary
process; i, iris; Ig, ligament of lens; m, ciliary muscle; opn, optic nerve; rt, retina;
sc, sclerotic coat; os, ora serrata.

oblique muscle arises from the sphenoid bone medial of the
optic foramen, extends along the medial wall of the orbital
cavity to its dorso-medial margin, where it passes through a
tendinous loop fastened to the frontal bone and then turns
laterad to its insertion in the sclerotic beneath the superior
rectus. The inferior oblique arises from the lachrymal bone
and is inserted on the sclerotic between the external and in-
ferior recti muscles. The above muscles may be demonstrated

248 ELEMENTS OF MAMMALIAN ANATOMY

by cutting away the lateral and dorsal walls of the orbital
cavity. The retractor oculi originates on the boundary of the
optic foramen and divides into four heads which are inserted
into the sclerotic around the entrance of the optic nerve.
This muscle is partly hidden by the recti muscles.

The eyeball is composed of three membranes and three
humors. The outer coat, the sclerotic, consists of the opaque
portion forming the caudal two-thirds, and the transparent
portion, or cornea, forming the remainder (Fig. 119). The
optic nerve pierces the sclerotic a little mediad of the longi-
tudinal axis of the eye. The surface of the cornea is more
strongly curved than that of the opaque portion of the sclerotic,
and contains no blood-vessels. The second or middle coat of
the eye is formed by the choroid membrane and its extension,
the iris. This coat is incomplete, as there is an aperture, the
pupil, through the iris for the admission of light. The choroid
appears as a jet-black membrane, less than half as thick as
the sclerotic, lying closely appressed to the latter. The choroid
is lined internally by dark pigment cells, except in the caudal
area around the optic nerve, which has a metallic luster. This
portion is called the tapetum. It causes the shining appear-
ance of the cat's eyes in the dark. The choroid is a vascular
membrane, being supplied by the ophthalmic artery, a branch
of the internal carotid.

The iris is attached by its peripheral margin to the sclerotic
and choroid coats, and hangs free in the aqueous humor. It
gives color to the eye. In the cat it is yellowish, while in man
it is frequently blue or black. The iris is merely a curtain to
regulate the amount of light admitted to the retina. There
is a sphincter muscle lying in it, which by contraction renders
the pupil very small. There is probably no dilating muscle
of the iris present in the cat. The short, thickened, radial
projecting folds of the choroid are the ciliary processes, which
contain numerous blood-vessels, and in some mammals a gland.
The ciliary muscle arises from the sclerotic coat near its junc-

THE NERVOUS SYSTEM 249

tion with the cornea, and is inserted into the cranial part of
the choroid coat.

The inner membrane of the eye is the rdma, which is of a
light gray color in a fresh specimen and seems quite free from
the choroid. It is thickest in the caudal two-thirds of the
cavity of the eyeball (Fig. 119). At the base of the ciliary
bodies it seems to end with a free margin, called the ora serrata.
In reality it becomes very thin here and is prolonged over the
ciliary bodies and covers the caudal aspect of the iris. The
blind spot is the point of entrance of the optic nerve, laterad
of which is the yellow spot, or macula lutea, containing the
fovea centralis, or acute point of vision. This is the point on
which the rays of light are focused when the cat sees distinctly.
The refracting media of the eye are the aqueous humor, the
crystalline lens, and the vitreous body. The aqueous humor is
a watery fluid occupying the cavity between the cornea and
crystalline lens. It always escapes as soon as the cornea is
punctured. The aqueous humor appears to be supplied by
the ciliary processes. The vitreous body is of a jelly-like con-
sistency, filling the part of the eyeball caudad of the lens. It
is perfectly transparent and is surrounded by a delicate cap-
sule, the hyaloid membrane.

The crystalline lens is a transparent biconvex tissue having
a vertical diameter of about one centimeter and a shorter
diameter through its optical axis. It is enclosed in a trans-
parent elastic capsule, some of whose fibers are continued
peripherad as the suspensory ligament which is inserted in the
choroid coat (Fig. 119).

The Auditory Organ. — The organ of hearing is composed of.
three parts — the external ear, middle ear, and internal ear.
The first consists of the pinna and the auditorius meatus exter-
nus. The auricle is the projecting portion of the ear cap-
able of being moved by muscles, and is composed of integument
strengthened by fibrocartilage. The auditorius meatus externus
extends from the base of the auricle to the tympanic membrane

250

ELEMENTS OF MAMMALIAN ANATOMY

(Fig. 1 20). Its outer or lateral third is formed by cartilage,
and the remainder by the tympanic portion of the temporal
bone (Fig. 18). The meatus is lined with mucous membrane
in which are numerous sebaceous and oleaginous glands. The
latter secrete the wax of the ear.

The middle car, or tympanum, is an irregular cavity about
one centimeter in diameter contained in the lateral chamber
of the bulla (Fig. 120). It is separated from the external
auditory meatus by the delicate translucent membrane, the
membra na tympani. The petrous bone containing the internal

ear forms part of the inner or
medial wall. In the petrous
bone are two foramina which
may be seen in a dry skull by
looking through the external
auditory meatus. The more
dorsal foramen is the fenestra
vestibuli, which in the recent
state is closed by a membrane

The internal ear is represented re- ^ • i i r . r j.i

moved about a centimeter from the tO whlch the foot of the StapCS

middle ear and slightly rotated to the -g attached. The ventral one

left. The base of the stapes, s, m

nature, covers the fenestra vestibuli, is the fenestra COcklcOS, also

ov, c, basal whorl of the cochlea: ea, i i i v • i.T_

external auditory meatus; eu, open- cloScd by a membrane m the

ing of the Eustachian or auditory reccut State. In the dry skull

tube; i, incus; in, malleus; sc, semi- m t

circular canals; ve, vestibule; /, the fenestra VCStlbull OpenS mto

tympanum. ^^^ ^^^^ ^^ ^^^^^ ^^^^-y ^f ^j^^

cochlea, and the fenestra coch-
leae opens into the vestibule of the internal ear. The auditory
tube (Fig. 19), whose opening may be seen craniad of the
tympanic bulla, connects the middle ear with the posterior
nares and thus admits air to the tympanic cavity.

To demonstrate further the anatomy of the middle ear, one
should clean the flesh from a fresh or preserved head and care-
fully cut away the ventral walls of both chambers of the tym-
panic bulla (Fig. 18).

Fig

120. — Diagram of the Mam-
malian Ear.

THE NERVOUS SYSTEM

251

In the middle ear are three bones, the malleus, incus, and
stapes, commonly called hammer, anvil, and stirrup. They
form a crooked chain across the cavity. The long process of
the malleus is fastened throughout nearly its whole length to
the inner surface of the membrana tympani, and its enlarged
extremity articulates with the body of the incus. The latter
has two legs, to one of which the stapes is attached. The base
of the stapes is inserted in the membrane closing the fenestra
vestibuli (Figs. 18 and 120).

The internal ear, or labyrinth, consists of three parts — the
vestibule, cochlea, and semicircular canals (Figs. 19 and 120).
All of these parts are of membrane and lie in cavities of corre-
sponding shape within the petrous bone. A lymphoid, periotic

Fig, 121. — Section of the Cochlea of the Calf. X 10. {From Ellenberger,

after KoUiker.)
a, Modiolus; c, scala tympani; v, scala vestibuli; hn, lamina spiralis; pt, portion
of the petrous, bone; r, scala media, or ductus cochlearis.

fluid, the perilymph, floats the delicate membranous internal
ear within its bony cavity, while within the membrane is a
similar fluid, the endolymph. The vestibule is a small sac adja-
cent to the tympanum, and may be seen by looking through
the fenestra vestibuli. From the dorso-caudal aspect of the
vestibule, arch three semicircular canals at nearly right angles,
to one another. The external semicircular canal is in a hori-
zontal plane and surrounds a small fossa almost caudad of the

252 ELEMENTS OF MAMMALIAN ANATOMY

fenestra vestibuli. The superior semicircular canal lies in a
transverse plane cautlad to the preceding. The posterior semi-
circular canal lies in a vertical longitudinal plane, immediately
laterad from the jugular foramen.

The cochlea is a coiled canal lying within the coiled cavity,
the bony cochlea, extending craniad from the vestibule. If
both chambers of the tympanic bulla are removed and a bristle
thrust into the fenestra cochleae (Fig. 18), it will enter the basal
whorl of the bony cochlea. A line drawn from the lateral
margin of the foramen vestibuli to the medial margin of the
fenestra cochleae passes through the apex and middle of the
base of the cochlea, which may be rendered visible by care-
fully clipping off with the bone-forceps the ventral portion of the
petrous bone along the line indicated. This coiled canal, the
cochlea, is divided into two channels by a shelf of bone, the
lamina spiralis, projecting from the central axis or modiolus of
the coil (Fig. 121). The bony lamina extends but partly across
the canal, the remaining distance being bridged by membrane.
The cranial channel, or the one nearer the apex of the cochlea,
is called the seal a vestibuli. The other is the seal a tympani.

The semicircular canals probably have nothing to do with
hearing, as they are well developed in fishes, some of which do
not hear at all. They may aid in helping the cat to maintain
its equilibrium. The auditory nerve, however, is distributed
to the vestibule and semicircular canals as well as to the cochlea
upon the lamina spiralis, where the organ of Corti, the essential
organ of hearing, is located.

REMARKS ON THE MAMMALIAN NERVOUS SYSTEM

So far as known, the relation of the sympathetic to the pe-
ripheral and central nervous systems is the same in all mammals.
The number of spinal nerves varies with the number of vertebrae.
The distribution of these nerves, however, is approximately
the same in all forms with five digits. In those having a less
number of digits the nerve branch corresponding to the lacking

THE NERVOUS SYSTEM

253

digit or digits is wanting. The arrangement of the columns or
tracts of fibers in the spinal cord is very similar in all the orders.
The anterior or direct pyramidal tract, however, is partially or
wholly absent in most orders below the Primates. It is best
developed in man, although in a number of cases it has been
found entirely wanting in the human. The number of the
cranial nerves is always twelve and their distribution is very
similar in all forms investigated.

The structure of the brain in the Ornithodelphia and Didel-
phia differs considerably from that of the Monodelphia. In the
two former subclasses the corpus callosum and fornix are very

Fig. 122. — Photograph of the Human Brain from the Lateral Aspect.

Two-fifths natural size.

rudimentary, but the anterior commissure piercing the corpora
striata is unusually large. The fibers, which in the Monodel-
phia arise from the cells of the hippocampus, and extend craniad
to form the fornix, cross transversely to the opposite hippocam-
pus in the two lower subclasses.

In all higher mammals the cerebrum is greatly convoluted,
but in the lower ones the convolutions are few or almost absent,

254

ELEMENTS OF MAMMALIAN ANATOMY

as in Ornithorhynchus. The above-mentioned features show
that the ornithodclphian brain presents a striking similarity to
the brains of reptiles and birds. The brains of Rodentia possess
but few convolutions, while the brain of man is the most highly
convoluted.

The size of the brain varies widely. As a rule, the larger the

brain in proportion to the size
of the animal, the greater is
its intelligence. However, in
man there appears to be but
slight connection between size
of brain and intelligence, as an
individual with a small brain
may be much more capable
mentally than one with a large
brain. Mental power in man
seems to depend upon the
development of the cells and
libers of the brain.

The average weight of a male
human brain is about three
pounds; of a female, about two
and two-thirds pounds. The
human brain is J-^4 the weight
of the body; the ape's, J^g; the
rat's, J^2; the sheep's, 1^51;
and the elephant's, ^500- The brain of man is larger than
that of any other mammal except the whale and elephant.
The brain of a large whale weighs over four pounds, while that
of a large elephant will weigh about ten pounds.

LABORATORY STUDIES AND SUGGESTIONS

1. How many nerves transmit the stimuli received by the organs of special
sense?

2. Where are the sense organs of pain located?

Fig. 123. — Brain of the Rabbit
FROM Dorsal Aspect.

THE NERVOUS SYSTEM 255

3. How many sense organs are visible in the mesentery of your specimen?

4. Through which nerve roots would the stimuli received by the cutaneous
sense organs pass into the cord?

5. Describe the nerves transmitting the stimuli from the olfactory organ.

6. Describe the gland secreting the tears and how they reach the nasal
cavity.

7. By cutting away the lateral and dorsal walls of the orbit dissect the mus-
cles of the eyeball and make a drawing of them, labelling all parts.

8. What nerves control the movements of the eyeball?

9. Procure the eyes of any mammal from the butcher-shop or slaughter-
house; bisect one in the meridional and the other in the equatorial direction.
Make a drawing of the features seen and label.

ID. Remove the crj-stalline lens from a fresh eye, describe its size, shape,
structure, length of focus, and power of magnification.

11. Describe the path of a stimulus from the retina to the area of sight in
the brain.

12. Name every feature visible in the eyes you have dissected.

13. What ner\'e supplies the auditory organ?

14. Describe the middle ear.

15. In what part of the temporal bone is the internal ear located?

16. By looking into the auditorius meatus of the dried skull two openings
are seen. Into which portions of the internal ear do these lead?

17. Write a description of the internal ear.

18. Mention some important points of difference in the nerv'ous system of
various mammals.

19. What relation, if any, between intellectual ability and brain development?

(iLOSSARY

Ab du' cens {ah, from; duccns, leading): the sixth cranial nerve.

Ab due' tor (<//>, from; diico, I lead): a muscle drawing a part outward.

Ac e tab' u lum (small cup): cavity of the innominate bone for articulation with

tin.' femur.
A cro' mi on (summit of shoulder): name of certain parts at the shoulder.
Ad: a Latin prefix of words; signifying to, toward or at.
Ad due' tor {ad, to; diico, I draw): a muscle drawing a part inward.
Af' fer ent {ad, to; f cro, I carry): the name of a nerve carrying an impulse to

the brain or cord, and also applied to a vessel conveying fluid to the organ

in which a physiologic process is to occur.
An aes thet' ic (want of feeling): any drug which when used externally or inter-
nally causes loss of feeling.
Al i sphen' oid {ala, wing; sphcn, wedge; old, like): the wing-like part of the

sjihcnoid bone.
Al ve' 0 lar {alveolus, small hollow) : relating to the sockets of the teeth.
Al ve' 0 lus : the socket of a tooth.
Am' bu la tory : slow-moving, walking.
Am phi ar thro' sis {am phi, around; arthron, a joint): a joint in which there is

limited movement in every direction.
Am phib' i ans {am phi, both; bios, like): a class of vertebrates including frogs

which spend part of the life in water and part on land.
A nas to mo' sis: the intercommunication of vessels.
An chy lo' sis (stiff joint) : a firm union of the bones forming a joint.
An' nu lar (annulus, a ring): a name given to the encircling ligaments at the

wrist and ankle.
Ap o neu ro' sis {apo, from; nctirou, a tendon): a membranous expansion of a

tendon.
A rach' noid (like a spider's web) : the delicate middle membrane enveloping the

brain and spinal cord.
Ar bo re' al : tree-climbing.

A re' o lar (open space) : relating to connective tissue loosely woven.
Ar ti dac' ty la (cven-fingered) : those ungulates having an even number of digits

on each foot.
A ryt' e noid {arylaina, pitcher; oid, like): the name of a pair of cartilages of the

larynx.
Au ric' u lar {auricula, outer ear): relating to the ear.

Au' dit o ry {and ire, to hear): pertaining to the act or the organs of hearing.
Ax il' la {axilla, armpit).

Ax' ilia ry: a name given to several structures in the region of the armpit.
Ax' one : the process which carries the impulse away from a nerve cell.

256

GLOSSARY 257

Bi' ceps (bis, twice; caput, head): a term applied to muscles having two origins.

Brach {hrachiiun, arm).

Brach' i al: a name given to several structures in the upper arm region.

Bra c' by ceph' aly : short-headed.

Bron chi: plural of bronchus.

Bron' chus {bronchos, windpipe) : one of the two tubes into which the trachea

divides.
Buc' cal (bucca, cheek) : pertaining to the cheek.

Ce' cum (blind) : first part of large intestine.

Cal ca' ne um {calcancum, the heel) : the os calcis or heel-bone.

Cal lo' sum (callosus, thick-skinned): the largest commissure of the brain.

Can a lie' u li : the small canals opening into the lacunae of bone.

Can' nu la {canna, a tube) : a small tube.

Ca pit' u lum {capiluliim, a small head) : the enlarged terminal portion of an
organ.

Car' di ac {kardia, the heart) : pertaining to the heart.

Ca rot' id: the chief artery lying on either side of the windpipe.

Car pal (karpos, wrist) : pertaining to he wrist.

Cau' dad : toward the tail.

Cau' dal {caiida, tail): relating to the tail.

Cen' tnrni: the body of a vertebra.

Ceph' a lie {kephala, head): relating to the head.

Cer a to hy' al : a part of the hyoid apparatus.

Car' vie al (cervix, neck) : a name applied to structures in the region of the neck.

Cer' vi dae : the name of the deer family.

Chev' ron bones : the bones on the underside of some of the caudal vertebrae.

Chi' asm (ki' azm, mark crosswise) : the optic commissure.

Chi rop' te ra (cheir, hand; ptcron, wing) : an order of mammals including the bats.

Cho an' ae : the posterior nares.

Cho' roid: the middle lining of the eyeball.

Cir cum val' late (circumvallcrc, to surround with a wall) : see vallate.

cut' or is : a small erectile organ occupying the same relative position in the
female as the penis occupies in the male.

Coc' cyx (kokkux, the cuckoo, resembling the bill) : the several united vertebrae
forming the tail in man.

Coch' le a (kok' le ah) (kochlos, a conch-shell): the coiled canal of the internal ear.

Ce' il ac (se' le ak) {koilia, belly) : a name applied to a large artery and a nerve
plexus in the abdomen.

Ce' lom {se' lum) : the body cavity.

Con' dyle {kondulos, a knuckle) : a paired rounded eminence of a bone for articu-
lation.

Cor' nu (a horn) : a name given certain structures resembling a horn.

Cor' nu a : the plural of cornu.

Cor' 0 noid {corona, crown; old, like).

Cor' por a {corpus, body) : plural of corpus. Corpora quadrigemina.

258 ELEMENTS OF MAMMALIAN ANATOMY

Cor' pus: a name given to the main portion of an organ. Corpus caliosum.

Cos' ta {cosia, rib).

Cos' tal : pertaining to the ribs.

Cot' yl old {kolula, a cup; oid, like): relating to the articular cavity in the in-
nominate bone.

Cra' ni ad: toward the plane in front of the cranium and perpendicular to the
spinal axis.

Cra' ni al : pertaining to the cranium.

Cra' ni iim: those bones of the skull encasing the brain.

Cru' ra: plural of crus.

Cms {cms, a leg): the part of the leg between the knee and ankle. It is also
applied to structures resembling the leg.

Cu' bold (like a cube) : one of the tarsal bones.

Cu ne a' tus (kuncus, a wedge) : a fiber tract in the spinal cord.

Cu ne' i form (wedge-shaped): bones of the ankle and wrist.

Cur so' ri al : fitted for running.

Cu ta' ne ous {cutis, the skin) : relating to the skin.

De cus sa' tion {dccussatus, crossed) : an oblique crossing of the nerves.

Dem i fac' et {dcmi, ha.U; facet fc, little face): the articular surface on the body of

a vertebra for the articulation of half the head of a rib.
Den' drites {dendron, a tree) : the processes of a nerve cell which transmit the

impulse toward the cell-body.
Di aph' y sis {dia, between; pimein, to grow): the shaft of a long bone.
Di a ste' ma {diastema, a distance) : a space between any two consecutive teeth.
Di ar thro' sis {dia, throughout; arthrosis, articulation): a form of articulation

giving much freedom of motion.
Di dac' tyl : two digits as in deer, ox, etc.
Di del' phi a {dis, twice; delphus, uterus): an order of mammals including the

kangaroos and opossums in which a paired uterus is present.
Di en ceph' a Ion {dia, between; enchcphalos, the brain) : the tween brain formed

largely by the thalami.
Di gas' trie {dis, double; gasfcr, belly): the muscle depressing the lower jaw.
Dig 'it {digitus, a finger) : the name of a finger or toe.

Dig' iti grade : where foot rests only on the rows of phalanges, as in dog and cat.
Dig it or' um : of digits.
Diph' y 0 dont {diphyes, twofold; odous, tooth): mammals having two sets of

teeth.
Dis' tad : away from the axis of the body.
Dis' tal : the part farther from the axis of the body.
Do li cho ceph' aly: long-headed.
Dor' sad {dorsum, the back) : toward the line passing from head to tail along the

tips of the spinous processes.
Du 0 de' num {duodeni, twelve each): first part of the small intestine; in man it

is twelve finger-breadths.
Du ra ma' ter {durus, hard; mater, mother) : the outer membrane of the brain and

cord.

GLOSSARY 259

E den ta' ta {e, without; dens, a tooth): an order of mammals some of which

have no teeth.
Ef fer ent (effercns, carrying from) : the opposite of afiferent.
Em' bry o : the undeveloped young.
En ceph' a Ion (en, in; kcphala, the head): the brain.
En do mys' i nm {cndon, within; mys, muscle) : the extension of the perimysium

between the muscular fibers.
En' si fonn {ensis, sword; forma, form): the cartilaginous process at the caudal

end of the sternum. Xiphoid process.
Ep i did' y mis (epi, upon; didymos, the testes): the contorted tubule forming

the small body lying against the testis.
Ep i mys' i um {epi, upon; mys, muscle): the delicate membrane enveloping

muscle.
E piph' y ses {cpi, upon; phyo, to grow): a process of bone attached for a time

to another bone by cartilage, but later becoming firmly united to it.
Ep i the' li una. : the outer layer of the skin and all mucous surface.
Eth' moid (ethmos, a sieve; old, like): the bone at the root of the nose.
Eu sta' chi an (u sta' ke an) (named after the anatomist Eustachio, 1500- 15 70).

Sometimes applied to auditory tube.
Eu the' ria {eus, good; titer ion, beast): a subclass including all mammals above

the marsupials.

Fa bel' lae : sesamoid bones in tendon of gastrocnemius muscle.

Fac' et {jacette, a little face) : a small plane surface usually on a bone for articu-
lation.

Fal lo' pi an tube: the canal conducting the eggs from the ovary to the uterus.
Uterine tube.

Fal lo' pi us: a noted Italian anatomist (1523-1562).

Fas' ci a (fash' e ah) : the membranous fibrous covering of muscles.

Fas cic' u lus (fascis, a bundle) : a little bundle of fibers forming part of a nerve
or muscle.

Fau' ces (faw' sez) : that part of the throat surrounded by the palate, tonsils and
uvula.

Fe nes' tra (a ■window).

Fir i fonn (fihim, ihrea.d; forma, form): name of papillae on tongue.

Fo ra' men (forare, to pierce) : a passage or opening, usually in bone, for the trans-
mission of nerves or vessels.

Fo ram' i na : the plural of foramen.

For mal' de hyde : an excellent disinfectant.

For' mal in : a 40 per cent, solution of formaldehyde in water.

For' nix (an arch) : the projecting bundle of fibers from the gyrus hippocampus,
beneath the corpus callosum.

Fos' sa (a ditch) : a depression or furrow.

Fos so' ri al : digging or burrowing.

Fu nic' u lus (funis, a cord) : applied to various cord-like structures.

26o ELEMENTS OF MAMMALIAN ANATOMY

Gas' trie ii^oslrr, stomach) : relating to the stomach.

Gas troc ne' mi us {giislrr, stomach; kncma, leg): large muscle in the calf of the

leg.

Gen' e ra: plural of genus.

Ge nic u la' tiun {gcuicularc, to bend the knee) : a name applied to certain bodies
in the brain.

Gen' us: a species or collection of species marked by one or more common char-
acteristics distinguishing them from other groups.

Ging' ly mus {ginglymos, a hinge) : a kind of joint having free motion in two
directions.

Glen' Did {glctia, a cavity; oid, like): pertaining to a shallow cavity.

Glis' sant: gliding as in flying squirrel.

Glos' sa: the tongue.

Glu' te al : pertaining to the buttocks.

Glu' te us {gloutos, buttock) : one of several muscles, gluteus maximus, etc.

Gly' CO gen (gltikos, sweet) : animal starch.

Grac' i lis (slender) : the name of a muscle in the leg.

Gy' ri : plural of gyrus.

Gy' rus {gyros, a circle) : a convolution of the brain.

Hal' lu cis (from hallux, the great toe).

He pat' ic (Jtepar, liver) : pertaining to the liver.

Het' er o dent {hcteros, other; odous, tooth) : having teeth of more than one kind.

Ho moi o ther' mal : preserving a uniform temperature, as in warm-blooded

animals.
Horn' o dent {homos, the same; odous, tooth): having teeth all of one form.
Hy' oid : the name of the bone at the root of the tongue.
Hy' po : under.

Hy po gas' trie : under the stomach.
Hy po glos' sus : under the tongue.

In' fra: below.

In fra or' bit al : under the orbit.

II' e um {cilo, twist) : the last part of the small intestine.

II' i ac {ilia, the flanks) : pertaining to the region of the ilium or hip bone.

In' guin al {in' gwin al) : pertaining to the groin or ventral region where the

pelvic limb joins the body.
In' ter: a Latin prefix meaning between.
In ter cos' tal : between the ribs.
In ter os' se ous : between the bones.
In ter ver' te bral : between the vertebrae.
Is' chi um {is' ki um) : the middle part of the innominate bone.

Je jun' um {jcjunus, empty) : the two-fifths of the small intestine extending
between the duodenum and ileum.

GLOSSARY 261

Ju' gal (njgutn, a yoke) : the malar bone.

Ju' gu lar (jugulum, throat); the name of the large veins in the neck.

Lac' er iim (laceros, torn): name of foramina in the skull.

Lach' ry mal (lachryma, a tear) : pertaining to the lachrymal apparatus.

Lac' te als {lac, milk): the lymphatics of the small intestine which take up the
chyle and carry it to the thoracic duct.

Lamb doi' dal (after a Greek letter) : pertaining to the suture between the parie-
tal and occipital bones.

Lam' i na (a plate or scale) : a term designating a thin layer of tissue.

Lar' 3mx: the cartilaginous tube at the cranial end of the trachea.

Lat' er ad {lalus, side; ad, to): toward one side.

Lat' er al : pertaining to the side.

La tis' si mus (broadest) : a name applied to certain muscles.

Le va' tor (a lifter) : a name given to muscles which raise parts.

Lin' gual (lingua, tongue): pertaining to the tongue.

Lum' bar {lumhiis, the loin) : relating to the region of the loins which is the lower
part of the back.

Lym phat ics {lympha, water): the absorbent system.

Mag' nimi (great).

Ma' lar {mala, cheek).

Mal le' 0 lus {malleus, hammer) : a process of bone.

Mal pigh' i: an Italian anatomist (1628-1694).

Mam ma' li a {mamma, breast): the highest class of vertebrates.

Ma nu' bri um (a handle) : the cranial piece of the breastbone.

Ma' nus (hand) : the hand.

Mar su pi a' li a {marsupos, a pouch) : a subclass of mammals having a pouch
beneath the belly in which they carry the young.

Ma' ter (mother): one of two membranes covering the brain.

Mas' toid {mastos, breast; old, like): the process of bone behind the ear.

Me a' tus (passage) : a channel or canal.

Me' di ad {medius, middle) : toward the middle.

Me' di al : pertaining to the middle.

Me di as ti' ntun (standing in the middle) : the space between the lungs, includ-
ing the heart and other organs.

Me dill' la {medidla, marrow) : the inner portion of an organ; the marrow of bone;
a portion of the brain (medulla oblongata).

Men in ge' al {tncninx, membrane): pertaining to the membranes of the brain or
cord.

Men' tal {mcntum, chin) : pertaining to structures about the chin.

Mes ati ceph' aly: medium-headed, as in taper.

Mes en ter' ic {mcsos, middle; cnteron, intestine): pertaining to the mesentery.

Mes' en ter y : a fold of the peritoneum joining parts of the intestine to the dorsal
part of the abdominal cavity.

262 ELEMENTS OF MAMMALIAN ANATOMY

Met' a (be^-ond).

Mes en ceph' a Ion {mcsos, middle; encephalon, brain): the mid-brain, consisting

of tb ^ corpora quadrigemina and crura cerebri.
Met en ceph' a Ion : the pons VaroUi and cerebellum.
Mo di' 0 lus : the central pillar or axis of the cochlea.
Mo no dac' tyl : one-toed, as in horse.
Mon' 0 phy dont {monos, single; phyo, grow; odoiis, tooth): having only one set

of teeth during life.
Men 0 tre' ma ta {monos, single; tremos, hole): the lowest subclass of mammals.

The intestinal and urinary products are voided through one opening as in

birds; duck bill and spiny ant eater.
Morphorogy {morpha, form; logos, discourse): that part of biology dealing

specially with form and structure.
My el en ceph' a Ion {myelos, marrow; encephalon, brain) : the medulla oblongata.
Mo' tor {movcrc, to move) : a name given nerves stimulating muscles.

Na ta tor' i al : amphibious, aquatic, swimming.
Neu' ral {neuron, nerve) : pertaining to a nerve.
Neu' rone : a nerve cell with all its processes.
Nu' clei : plural of nucleus.

Nu' cle us i^nux, a nut): the essential part of every cell; also applied to a definite
bunch of nerve cells.

Ob' tu ra tor : the name of the large foramen in the coxal bone or of structures

near to it.
Oc cip' i tal (06, against; caput, the head): relating to structures in the region of

the back part of the head.
Oc' u lar (oculus, the eye) : pertaining to the eye.
O don' toid {odous, tooth; oid, like) : relating to the tooth-like process of the axis.

Dens.
Oid: a common suffix derived from Greek eidos and signifying like.
Olec' ran on {olea, elbow; kranion, head): process of the ulna.

0 men' turn: a fold of the peritoneum connecting the abdominal viscera.

01 fac' to ry {olfacere, to smell) : pertaining to the nose.
Oph thai' mic {ophthalmos, eye): p rtaining to the eye.
Op tic {opiikos, to see) : relating to the eye.

O' ra: mouth.

Or' bit al {orhis, circle) : pertaining to the cavity for the eye.

Or' gan : any part having a definite function.

Or nith o del' phi a {ortiis, bird; delphus, womb): the oviparous mammals.

Os: bone.

O' va : plural of ovum.

O va' le : oval.

O vip' a rous {ovum, egg; par ere, to bring forth): those animals which deposit

eggs instead of bringing forth living young.
O' Vum: egg.

GLOSSARY 263

Pa ri' e tal (paries, a wall).

Par of id (para, near; ous, ear): the name of a salivary gland.

Pec' to ral {pectus, breast): pertaining to structures in the region of the breast.

Ped' i cles {pediculus, a little foot) : the foot of the neural arch.

Pe' dun cles {pedunctilus, a little foot) : bands of fibers uniting certain parts of the
brain.

Pel' vie : relating to the cavity between the innominate bones.

Pent a dac' tyl : five-toed, as in phenacodus, etc.

Per i mys' i um {peri, around; mus, a muscle): the tissue which envelops the
primary bundles of muscle fibers.

Per is so dac' ty la {perissos, odd; dactyl, finger) : those ungulates having an odd
number of digits.

Pe riph' e ral : pertaining to the outside.

Per i to ne' um {peri, around; teinein, to stretch) : the serous membrane lining
the abdominal cavity and surrounding most of the organs within it.

Per o ne' al {perone, a pin) : relating to the fibula.

Pe' des : plural of pes.

Pes: foot.

Pha Ian' ges: plural of phalanx.

Phal' anx : one of the bones of the fingers or toes.

Phar' ynx (throat) : the cavity back of the mouth.

Phren' ic {phren, diaphragm) : pertaining to the diaphragm,

Phy log' e ny {phyla, tribe; genas, producing): that science treating of the evo-
lution of a group.

Pi' a ma' ter (soft mother) : the delicate membrane next to the brain and cord.

Plan' ti grade : where entire sole of foot or hand rests on ground, as in the hind-
foot of the bear.

Pneu mo gas' trie {pnenma, air; gaster, stomach): the vagus nerve.

Poi kil 0 ther' mous: bodily temperature varying with surrounding medium, as
in cold-blooded animals.

Pons: bridge. Pons Varolii.

Pop lit' e al {poples, knee) : pertaining to the caudal region of the knee-joint.

Post: a common prefix meaning after or behind.

Pri ma' tes {primus, first) : the highest order of mammals, including man and the
monkeys.

Pro fim' da {profundus, deep) ; a term given to a part deep-seated.

Pro to chor da' ta {prolos, first; chorda, cord): those forms between the inverte-
brates and vertebrates. Seasquirts.

Pro to the' ri a {protos, first; ther ion, beast): the oviparous mammals.

Prox' i mad : toward the central axis of the body.

Prox' i mal : that part nearest to the central axis of the body.

Pter' y goid {pteron, wing; oid, like) : part of the sphenoid bone.

Pul' mo na ry {pulmo, lung) : pertaining to the lung.

Py lor' us : {pyloros, gate-keeper) : the opening of the stomach into the duodenum.

264 ELEMENTS OF MAMMALIAN ANATOMY

Quad' ri ceps {quadri, four; caput, head).

Quad ri gem' i na: plural of quatlrij^cminum.

Quad ri gem' i num (quaJri, four; gcminus, twin born): part of the brain.

Ra' mi: plural of ramus.
Ra' mus : the branch of an organ.

Rec' ti grade: where weight of foot rests on large pad; as in elephant.
Rec' tus: straight.
Rhin' al: pertaining to the nose.
Ro Ian' do : an anatomist.
Ro tun' dum: round.

Ru' mi nant [niniiuarc, to chew the cud): any of the ungulates which chew the
cud.

Sa' crum {sacer, sacred) : the part of the backbone between the coxal bones.
Sag' it tal {sagitlii, an arrow) : a name given to a vertical longitudinal plane of the

body.
Sal ta tor' i al : leaping.

Scaph' oid {skapha, a boat) : a bone in the wrist and also the ankle.
Sci at' ic {si at' ic) : relating to structures in the region of the ischium.
Scle rot' ic (skleros, hard): relating to the outer coat of the eye.
Se ba' ce ous (sebum, suet or fat) : the name of glands in the skin.
Sec to' ri al (stcare, to cut) : the carnassial or last premolar tooth in many of the

carnivora.
Sem i lu' nar (semi, half; luna, moon).

Semi plan' ti grade : where half the sole rests upon the ground; fore-foot of bear.
Ses'amoid (sesamo?!, a grain: oid, like): the name of small bones developed in

tendons.
Sig' moid: shaped like the Greek letter sigma.
Si' nus (sinus, a hollow): a cavity or channel.
So' le us (flat): a muscle of the calf of the leg.

Sper mat' ic (sperma, seed) : pertaining to the reproductive fluid called semen.
Sper ma to zo' a (sperma, seed; zoa, animals): plural of spermatozoon.
Sper ma to zo' on : the male reproductive cell developed in the testis.
Sphen' oid: (sphen, wedge: oid, like): as the sphenoid bone.
Sphinc' ter (to squeeze) : the name of a muscle surrounding and capable of closing

an orifice.
Splanch' nic : pertaining to the viscera.
Sub: a common prefix denoting under or beneath.
Sty' loid (stylos, a pillar).
Sudoriferous (sudor, sweat).
Sudoriparous (sudor, sweat; parcrc, to produce): secreting sweat.

GLOSSARY 265

Su' pra: a prefix denoting above.

Sul' ci: plural of sulcus.

SuK cus {sulcus, a furrow): a cleft or furrow in the brain.

Syl' vi us: a noted anatomist.

Sjrm' phy sis (sym, together; pliyo, grow): the junction of bones usually in the

median line of the body.
Syn ar thro' sis (syn, together; arthron, a joint): a form of articulation in which

the bones are immovably united.
Sys' tern: a collection of organs for one general purpose.

Tel en ceph' a Ion {Idos, end : cncephalon, brain) : the cerebral hemispheres and

corpora striata; the end brain.
Te' res: round.

Tet ra dac' tyl : four-toed, as in hippopotamus and dog.

Thar a mus {thalamos, bed) : the thalami form the chief part of the tween brain.
Thy' reoid (Jhyrcos, a shield; old, like) : the name of structures in the region of the

thyreoid cartilage.
Tib' i al {tibia, shin) : pertaining to the tibia or shin bone.
Tri dac' tyl: three-toed, as in rhinoceros and early horse.
Tri' ceps {Ires, three; caput, head): a large muscle on the back of the arm.
Tri cus' pid : having three points or cusps. Tricuspid valve of the heart.
Tri gem' i nal : the fifth cranial nerve, so called because of its three divisions.
Tro chan' ter : the name of two processes on the femur.
Troch' le ar {trochilia, a pulley).

Tur' bin al : one of the turbinated or lateral ethmoid bones.
Tym' pan um {tympanum, a drum): the middle ear.

Um bil' i cus (navel) : the depressed cicatrix in the center of the abdomen mark
ing the hole giving passage to the vessels formerly connecting the young
with the mother.

Un' ci form {uncus, a hook; forma, form): a bone of the carpus.

Un gu la' ta {ungula, a hoof) : an order of mammals characterized by hoofs.

Un' gu li grade : where the foot rests only on the end of the phalanx, horse, deer.

U re' ter: the tube from the kidney to the bladder.

U re' thra : the tube from the bladder to the exterior.

U' ter us : the womb or cavity in which the young are developed.

Val' late : large papillae at the base of the tongue.

Ven' trad {venter, stomach): toward a plane passing along the underside.

Ver' te bra {vertere, to turn) ; a bone of the spinal column.

Ver' te brae : plural of vertebra.

Ves tig' i al: rudimentary; existing only as a trace.

Vis' ce ra : the organs within the body cavity.

Vo' lant: flying, as the bat.

266 ELEMENTS OF MAMMALIAN ANATOMY

Whar' ton: an Isnglish anatomist (i6ia-i67.0; name of the duct from the sub-
lingual gland.
Wil' lis: an anatomist (1621-1666).
Wir' sung: an anatomist ( 1643); name of a duct from the pancreas.

Xiph' oid : same as ensiform.

Zy go' ma {zyf^oma, cheek-bone): the arch formed by a process of the temporal
bone and the malar.

INDEX

Abdominal aorta, 154, 155
Abduccns nerve, 232
Acetabular (cotyloid) bone, 74

notch, 75
Acetabulum, 75
Achilles, tendon of, 103
Acoustic meatus, external, 42, 44

internal, 43, 46
Acromion process, 64
Air sacs, 191, ig6
Alimentary canal, 127

walls of, 139
Alisphenoid bone, 44, 45, 47
AUantois, 5
Alveolar ducts, 195

sacs, 195
Alveoli (lungs), 195
Amnion, 5
Amniota, 5
Amphiarthroses, 83
Amphibia, 5
Amphioxus, 4
Anamnia, 4
Anatomy, i
Anesthetizing, 10
Aorta, 153, 154

abdominal, 154, 155

arch, 154, 155

thoracic, 154
Appendix vermiformis, 139
Ac^ueductus cerebri, 215
Aqueous humor, 247, 248
Arachnoid, 209, 225
Arbor vitae, 216, 224
Arch, aortic, 154, 155

development of, 174

zygomatic, 35, 42
Arm, arteries, 160

articulation, 83

bones, 63

Arm, muscles, 94
nerves, 234, 236
veins, 168
Arteries, 154

development, 174
head and neck, 157
hind limb, 162
names, adrenolumbar, 156
alveolar, inferior, 158
anonymous, 154
anastomotica magna, 161
articularis genu suprema, 164
auricularis posterior, 158, 159
axillaris, 160

basillaris (basilar), 158, 159
brachialis (brachial), 160, 161
bronchiales (bronchial), 155
carotis communis (common
carotid), 157, 158, 159
externa, 158, 159
interna, 158, 159
caudalis (sacralis media), 157
celiac, 155
cerebellar, anterior, 158, 160

inferior posterior, 160
cerebral, anterior, 160
medial, 158
posterior, 158, 160
circumflex, femoral, lateral, 164,
169
humeral, anterior, 161
posterior, 161
colica dextra (right colic), 156
media (middle colic), 156
sinistra (left colic), 157
collateral radialis superior (su-
perior radial lateral), 161
ulnaris superior, 161
coronaria (coronary), 154
costocervical axis, 160

267

268

INDEX

Arteries, di^italcs dorsales (dorsal
digital), 162
plantaris (plantar digital), 165
epigastrica inferior, 163
esophageal, 155
femoralis (femoral), 163, 164
gastrica sinistra (left gastric),

155
gastroduodenalis (g a s t r o -

duodenal), 156
gastroepiploica dextra (right

gastro-epiploic), 156
genital (spermatic, ovarian),

155, 157
genu suprema, 164
glutea inferior (inferior gluteal),
164

superior (superior gluteal),
164
hemorrhoidalis media (medial

hemorrhoidal), 164
hepatic, 156
hypogastric, (internal iliac),

155, 164
ileocolic, 156
iliaca externa (external iliac),

157, 169
interna (internal iliac, hypo-
gastric), 15s, 157, 169
iliolumbalis (iliolumbar), 155,

157, 169
infraorbital, 158, 159
innominate (anonymous), 154,

i55> 157, 169
intercostal, 155
interosseae (anterior, posterior),

162
lienalis (splenic), 156
lingual, 158, 159
lumbales (lumbar), 155
lumboabdominalis (adrenolum-

balis), 156
malleolaris anterior lateralis
(external malleolar), 164

anterior medialis (internal
malleolar), 164

Arteries, mammaria interna (internal

mammary, sternal), 160

maxillaris externa (external

maxillary, facial), 15S, 159

interna (internal maxillary),

159

meningea media (middle men-
ingeal), 159

mesentcrica inferior (inferior
mesenteric), 155
superior (superior mesen-
teric), 155

occipital, 158

oesophageae (esophageal), 159

ophthalmic, 159

ovarian, 155

palatina descendens (descend-
ing palatine), 158

pancreaticoduodenalis inferior
(inferior pancreaticoduo-
denal), 156
superior (superior pancrea-
ticoduodenal), 156

peroneal, 164

phrenic, 156

plantar arch, 165

popliteal, 164

profunda brachii (superior pro-
funda), 161

profunda femoris (deep
femoral), 163

pulmonary, 154

pyloric, 156

radialis (radial), 160

recurrens (radial recurrent),
162

renal, 157

sacralis media (caudal), 157

saphenal, 164

spermatic, 157

sphenopalatine, 159

spinalis anterior, 158

splenic (lienalis), 156

subclavian, 160

submental, 169

subscapular, 160, 169

INDEX

269

Arteries, superior profunda (profunda
femoris ), i6i, 169
suprascapular, 161, 169
temporalis superficialis (super-
ficial temporal), 159
thoracica anterior (anterior
thoracic), 160
longa (long thoracic), 160,
169
thoracodorsalis (dorsal

thoracic), 160, 169
thyreoid axis, 160
thyreoidea ima (lowest thy-
reoid), 159, 169
inferior, 159, 169
superior, 159
tibialis anterior, 164

posterior, 164
transversa colli (transverse

artery of the neck), 160
transversa scapulae, 160
ulnaris (ulnar), 162
recurrens, 162
collateralis superior, 161
umbilical, 147
vertebral, 159, 160, 169
volar, 162
thoracic limb, 160
trunk, 154
Articulations, 83

amphiarthrodal, 83
atlanto-occipital, 36
diarthrodal, 83
Artiodactyla, 8
Arytenoid cartilage, 197
Atlanto-occipital articulation, 36

membrane, 36
Atlas, 54

Atrium (heart), 150; (lung), 195
Auditory bulla, 37, 38

meatus, external (meatus acusti-
cus externus), 42
internal (meatus acusticus in-
ternus), 43
nerve (acoustic), 232
organ, 249

Auricle (ear), 249; (heart, atrium),

150, 151, 153
Axis (epistropheus), 56

Back bone, 53
Balanoglossus, 4
Basioccopital bone, 44, 45
Basisphenoid bone, 44, 45
Bicipital groove, 65

tubercle, 95
Bicuspid valve, 151
Bile, 144

cyst, 144, 148

duct, 138, 144
Bladder, 199
Blind spot, 249
Bloodvessels, 150

injection of, 9

Body cavity, 134

Bones, structure of, 19

ear, 250

head, 32

method of cleaning, 15
number of, 28
pelvic limb, 74
table of, 29
thoracic limb, 63
Brachial plexus, 234
Brachium conjunctivum, 218

pontis, 218
Brain, 219

arteries of, 158

basal ganglia of, 229

commissures of, 217

external features, 210

extraction of, 14

human, 253

internal structure of, 214

mammalian, 253

parts of, 210

rabbit's, 254

ventricles of, 214

weight of (in mammals), 254
Branchiostoma, 4
Bronchial tubes, 193, 195

270

INDEX

Bulbourethral glands, 213
Bulla, auditory, 42

tympanic, 37, 42, 44, 47

Calcaneous bone, 29, 79
Callosal sulcus, 189
Cambrian, 3
Canal, alimentary, 134

anterior palatine, 49

condyloid (posterior condyloid), 45

facial (aqueduct of Fallopius), 46

Hunter's, 164

hypoglossal (anterior condyloid),

45» 46
lachrymal, 50
nasolachrymal, 50
of Hugier, 37
posterior palatine, 49
pterygoid, 38
semicircular, 250, 251
Vidian (pterygoid), 38
Canine teeth, 130, 131, 132
Canthus, 246
Capillaries, 171
Capitate (os magnum), 29, 69
Capsular ligament, 84
Capsule, external, 222
internal, 221, 222
of lens, 259
Carboniferous, 3
Cardiac plexus, 241
Carnivora, 7

Carotid plexus (arterial), 159; (nerv-
ous), 241
Carpus, 67
Cartilages, 19
costal, 62
kinds of, 19
of larynx, 51
Caudate nucleus, 222
Cecum, 122, 139, 147
Celiac artery, 155
ganglion, 243
Celom, 134
Centrum, 53, 56
Ceratohyal, 51

Cerebellar, arteries, 160

hemispheres, 224
Cerebellum, 210, 223
Cerebral, aqueduct (iter, aqueduct of
Sylvius), 215

arteries, 160

fissures (sulci), 211

gyri (convolutions), 211

hemispheres, 211, 214

peduncles, 212

veins, 168
Cerebrum, 210, 211
Cerebrospinal fluid, 225
Cervical ganglia, 240

lymph glands, 183

nerves, 234, 235

plexus, 234, 235

vertebrae, 54
Cetacea, 8

Chambers of eye, 249
Chevron bones, 59
Chiasma, optic, 213
Chiroptera, 7
Choanae, 34
Chondrohyal, 52
Chordae tendinse, 151
Choroid plexus, 214
Ciliary, body, 248

folds, 248
Circle of Willis, 158, 159
Circumflex nerve, 207
Circumvallate papillae, 230
Classification, 2
Clavicle, 64
Clinoid plate, 46

process, 47
Clitoris, 201
Cloaca, 148, 207
Coats of eye, 247

testis, 205
Coccyx, 61
Cochlea, 252
Collateral ligaments, 84
radial artery, 161
ulnar artery, 161
Colon, 139

INDEX

271

Commissure habenae, 221
Condyle, occipital, 34, 36
of femur, 77
of tibia, 77
Condyloid canal, 45
Conjunctiva, 219, 246
Connective tissues, 18
Coracoid border, 64

process, 64
Cord, spinal, 225
Corium, 26
Cornea, 247, 248
Coronoid process, 50
Corpora, mammillaria, 213, 216, 2ii

quadrigemina, 219

striata, 219, 221
Corpus callosum, 217

cavernosa, 206

dentatum, 224

spongiosum, 206
Corti, organ of, 252
Costal cartilage, 62
Costocervical axis, 160
Cowper's glands, 203
Cranial cavity, 47
Cranium, 39
Cretaceous, 3
Cribriform plate, 47
Cricoid cartilage, 192
Crucial ligaments, 85
Crura, cerebelli, 218

of penis, 206
Crus, 78, 79
Crystalline lens, 249
Cuboid, 29

Cuneiform bones, 29, 80
Cutaneous sense organs, 244
Cuvier, duct of, 177, 179
Cyclostomes, 4
Cystic duct, 144

Deltoid ridge, 65
Dermis, 25
Devonian, 3
Diaphragm, 115
Diastema, 50, 51

Didelphia, 8

care of young, 8, 207
Diencephalon, 210
Digestive system, 127, 147
Digit, 71, 73, 81
Digital fossa, 76
Digitigrade, 73
Dinosaur, 6
Dipnoi, 5

Dissection, preparation for, 13
Duct of Cuvier, 177, 179
Ductus Botalli (ductus arteriosus),

154, 176
Dura mater, 209

Ear, 249

bones containing, 42

ossicles of, 250
Ectocuneiform (external cuneiform),

29, 80
Edentata, 7
Elbow-joint, 83
Embryology, i

circulatory system, 150
Eminence, iliopectineal, 75
Entocuneiform (internal cuneiform),

29, 80
Eocene, 3
Epicondyles, 65
Epidermis, 25
Epididymis, 205
Epiglottic cartilage, 192
Epiglottis, 192
Epihyal, 51

Epistropheus (axis), 56
Epithelium, 18

Epitrochlea (medial epicondyle, in-
ternal condyle), 65
Ethmoid, 40
Ethmoturbinals, 41
Eustachian tube (tuba auditiviij, 42,

134
Eutheria, 7
Excretory system, 19S
Exoccipital bones, 45
External occipital crest, 36

272

INDEX

External occipital protuberance, 36
Eye, 246

muscles of, 247

nerves of, 2^2, 233

structure of, 248
Eyeball, 247
Eyelids, 246

Face muscles, 107
Facet, articular, 57, 62

auricular, 74

costal, 57, 62

transverse costal, 57, 62

tubercular (transverse costal), 57,
62
Facial bones, 48

canal, 46

nerve, 233

vein, 168, 169
Fallopian (uterine) tube, 200, 201
False ribs, 6i

vocal cords, 192
Families, 8
Fascia, antibrachial, 92

cremasteric, 204

deep crural, 104

endothoracica, 135

intercolumnar (cremasteric), 204

lata, 98

lumbodorsal, 113

of back, 113

of thigh, 98

propria, 205
Fauces, 129
Feces, 24

Female genital organs, 200
Femur, 76
Fenestra cochleae (rotunda), 42, 250

ovalis (vestibuli), 42, 250

rotunda (cochleae), 42, 250

vestibuli (ovalis), 42, 250
Fibrocartilage, 19

intervertebral, 53
Fibula, 78

Filliform papillae, 130
Finger, bones of, 70

Finger, muscles of, 97
Fissipedia, 7

Fissura cerebri lateralis, 2n
Fissure of SyKius, 211

orbital, 47
Fissures of cerebrum, 211

spinal cord, 226
Floating ribs, 61
Follicles, Graafian, 202
Foot, bones of, 67, 79

muscles of, 105

of horse, 72, 81
Foramen, anterior palatine, 46

atlantal, 56

carotid, 44

ethmoidal, 41

hypoglossal, 46

incisivum, 38

infraorbital, 38, 49

interventricular (of Monroe), 229

jugular, 45, 46

lacerum, anterius (sphenoidal
sinus), 46
medium, 46

magnum, 47

mandibular, 51

mental, 51

obturator, 75

of Monroe (interventricular), 215,
229

optic, 46

ovale, 46
(heart), 153

rotundum, 37, 46

sacral, 75

sphenopalatine, 46, 49

stylomastoid, 44

supracondyloid, 65

transversum, 57

vertebral, 53
Foramina of skull, 46
Forearm, bones of, 63

bloodvessels of, 160

muscles of, 95

nerves of, 234
Formaldehyde, 9

INDEX

273

Formalin, 9
Formula for teeth, 133
Fornix, 216, 218
Fossa coronoid, 65

digital, 77

external pterygoid, 37, 48

glenoid, 63, 65

hypophyseal (sella turcica), 46

infraspinatus, 64

intercondyloid, 65

internal pterygoid, 37

jugular, 36

lateral pterygoid, 37

mandibular, 37, 42

masseteric, 51

median, 37

olecranon, 65

orbital, 40

ovalis, 153

radial, 66

rhomboidea, 223

scaphoid, 37

subscapular, 64

supraspinous, 64

temporal, 40

trochanteric, 77
Fovea centralis, 249
Frenulum lingus, 129
Fretum Halleri, 173
Frontal bone, 39

plate, 39

sinus, 39
Fundus of stomach, 136
Fungiform papillae, 130
Funiculus cuneatus, 223
lateralis, 223

of Rolando, 223
Funny bone, 237

Gall bladder, 137, 144
Ganglia, celiac, 243

semilunar, 242, 243

sympathetic, 240

thoracic, 241
Ganglion, stellate, 241

vagus, 241

Ganoids, 5
Gastric plexus, 242
Gastroduodenal ligament, 145
Gastrohepatic ligament, 145
Gastrolienal ligament, 146

omentum, 146
Gastrosplenic omentum, 146
Genera, 8

Geniculate body, lateral, 221
Genital organs, 198
Geological time, 3
Ginglymus (hinge-joint) 83
Gland, adrenal, 188, 189

Bartholin's, 205

bulbourethral, 203, 206

Cowper's, (bulbo-urethral), 203,
206

digestive, 147, 160, 162

ductless, 188

infraorbital, 143

lachrymal, 246

mammary, 203

molar, 143

oleaginous, 250

parotid, 143

prostate, 203

sublingual, 143

submaxillary, 143

thymus, 188, 189

thyreoid, 188, 189
Glands, Harderian, 246

inguinal (lymph), 183, 184

lymphatic, 183

Meibomian, 246

of mouth, 143

of stomach, 140

salivary, 143

sudiparous, 26

tarsal, 246
Glans penis, 206
Glenoid angle, 63

border, 63

fossa, 63
Glottis, 192
Gnathostomata, 4
Graafian follicles, 202

274

INDEX

Great omentum, 145

scapular notch, 64

sciatic nerve, 239
notch, 75

sigmoid cavity, 66

trochanter, 76

tuberosity, 65
Gustatory organ, 245
Gyri of cerebellum, 224

of cerebrum, 211
Gyrus ectosylvius, 211

fornicatus, 211

marginalis, 211

suprasylvius, 211

Hair, 26

Hamate bone (unciform or hooked

bone), 70
Hamular (hook) process (hamulus

pterygoideus), 37
Hand, bones of, 67

muscles of, 97
Harderian glands, 246
Hatteria (sphenodon), 221
Head, bones of, 33

muscles of, 107
Heart, 150

development of, 172

human, 151
Hemispheres of cerebellum, 224

of cerebrum, 210
Hepatic artery, 155

duct, 144

plexus, 242

veins, 167
Hind brain, 219
Hip-joint, 74
Hippocampus, 218, 219
Histology, I
Holocene, 3
Horns, 40

of uterus, 174
Horse, evolution , 67

limbs of, 67, 68, 69, 71, 72
Hugier, canal of, 37
Humerus, 65
Humor, aqueous of eye, 247, 249

Humor, vitreous (body) of eye, 247, 249

Hunter's canal, 164

Hyaloid membrane, 249

Hymen, 201

Hyoid bone, 52

Hypogastric plexus, 243

Hypoglossal canal, 46

foramen, 37

nerve, 232, 233
Hypophysis, 212

Ichthyopsida, 4
Ichthyosaur, 6
Ileocolic valve, 139
Ileum, 138
Iliac glands, 183
Iliopectineal eminence, 75

fossa, 75

line, 75
Ilium, 74
Incisor teeth, 131
Inferior cervical ganglion, 241

maxillary bone, 51

vena cava (postcava), 165
Infraorbital foramen, 38

gland, 143
Infraspinous fossa, 64
Infundibulum, 212
Inguinal canal, 205

glands, 183

ligament (Poupart's), 201
Injection method, 9
Innominate artery, 154

(coxal) bone, 74, 75

vein, 168
Insectivora, 7
Integument, 25

muscles of, 92
Intercondyloid fossa, 76
Intermediate cuneiform bone 29, 80
Internal capsule, 222

ear, 251
Interparietal bone, 43
Intertrochanteric line, 77
Interventricular foramen (of Monroe),

216
Intervertebral foramen, 53

INDEX

275

Intestinal glands, 140
Intestine, large, 139

small, 138
Invertebrata, 3
Involuntary muscles, 18, 19
Iris, 211

Ischiadicus nerve, 239
Ischium, 74

Jaw, lower, 51

upper, 48
Jejunum, 125
Joints, kinds of, 83

ligaments of, 84

structure of, 83
Jugular foramen, 37

ganglion, 186

notch, 36

process, 36

veins, 168, 169
Jurassic, 3

Labyrinth, 251
Lachrymal bones, 50

canal, 50

gland, 246

groove, 51
Lacteals, 141, 182
Lambdoidal ridge, 36
Lamina semicircularis, 222

spiralis, 252
Large intestine, 139
Larynx, 191

cartilages of, 192

muscles of, 1 1 1
Lateral cuneiform (ectocuneiform)
bone, 80

ventricles of brain, 215
Leg, arteries of, 162

bones of, 74

ligaments of, 84

muscles of, 98

veins of, 165, 169
Lens, crystalline, 249
Lenticulate nucleus, 222 '

Lesser curvature of stomach, 136
omentum, 145
palatine artery, 159
sciatic notch, 75
trochanter, 76
tuberosity of humerus, 65
Ligament, (s), (tum), 83, 146
annular, 95
Botalli, 154, 176
broad, 146, 210
capsular, 36, 84
collateral, 84
crucial, 85

duodenohepatic, 133
falciform, 146
flava, 85

gastroduodenal, 146
gastrohepatic, 146

gastrolienal (gastrosplenic), 146

iliosacral, 85

inguineal (Poupart's), 201

of bladder, 199

of hip-joint, 76

of liver, 145

of malleoli, 84

of minisci, 85

of ovary, 201

of patella, 78, 84

of skull, 36

of thoracic limb, 95

of uterus, 201

pelvic limbs, 84

Poupart's, 201

pulmonary, 195

round, 145, 201

suspensory, (eye), 249

suspensorium, 199

teres, 76
Linea aspera, 76
Liver, 144
Lumbar aponeurosus, 112

nerves, 237

plexus, 237, 238

vertebrae, 58
Lumbodorsal fascia, 1 1 2
Lumbosacral plexus, 238

276

INDEX

Lungs, 194

Lymph, 182

Lymphatic duct, 182, 185

development of, 187

glands, 182, 183

injection of, 13

system, 182

Macula lutea, 249

Magnum os, 29
Malar bone, 29, 51
Male genital organs, 203
Malleoli, ligaments of, 78
Malleolus, lateral, 78

medius, 78
Malleus, 250
Mammals, 6
Mammary glands, 203
Mammillary bodies, 212
Manatus, 59
Mandible, 51
Mandibular fossa, 37, 42

foramen, 51
Manubrium, 61
Manus (hand) bones of, 70

muscles of, 97
Marginal gyrus, 216

sulcus, 216
Marsupialia, 7, 217
Massa intermedia, 221
Mastoid process, 36
Maxillary bone, 48

external (artery), 158, 159

internal (artery), 159
Maxilloturbinal, 49
Meatus, external acoustic, 37
inferior, 43
internal acoustic, 43
Medial cuneiform bone, 80
Mediastinum, i68
Medulla oblongata, 196
Meibomian glands, 246
Membrana nictans, 246

tympani, 240
Membrane, anterior atlan to-occipital,
36

Membrane, interosseus, 78

mucous, 139

posterior atlanto-occipital, 36
Membranes, of brain, 209

of spinal cord, 225
Meninges, 219
Menisci, 85

ligaments of, 85
Mesencephalon, 210
Mesenteric ganglion, inferior, 242
superior, 242

glands, 182

plexus, 242
Mesentery, 146
Mesethmoid, 41
Mesocolon, 145
Mesocuneiform, 80
Mesogastrium, 145
Mesorectum, 145
Metacarpals, 70
Metacarpus, 70
Metacromion, 64
Metatarsals, 81
Metatarsus, 81
Metencephalon, 223
Midbrain, 219
Middle ear, 250
Miocene, 3
Mitral valve, 151
Modiolus, 251, 252
Molar gland, 143

teeth, 131
Mole, 221
Monodelphia, 8
Monotremata, 7, 207
Monroe, interventricular foramen of,

215
Morphology, i
Mouth, 129

glands of, 143
Mucous membrane, 129, 136, 139
Multangular, greater (trapezium), 68

lesser (trapezoid), 69
Muscles, 87

of abdomen, 112

of chest, 93

INDEX

277

Muscles, dissection of, 88
of fore limb, 84, 95, 96
of hand, 97
of head and neck, 109
of hind limb, 98
of hip, 98
kinds of, 19
of scapula, 94
of shoulder region, 92
structure, 19
of thigh, 98
of trunk, 112

abductor auris brevis, 107, (112)
longus, 107, (hi)
brevis pollicis, 97 (48)
caudae (coccygis) externus, 115,
(221)
internus, 115, (218)
cruris, loi, (58)
digiti quinti, 98 (53)

brevis, 105, (99)
digiti secundi, 98, (51)
medius digiti quinti, 105, (96)
accelator urinae, 124, (233)
acromiodeltoideus, 94, (18)
acromiotrapezius, 93, (4)
adductor auris inferior, 108, (118)
digiti quinti longus, 105, (100)
femoris, 102, (71)
quinti (opponens), 98, (55)
secundi, 98, (52)
longus, 102, (74)
medius, 108, (122)

digiti quinti, 105, (97)
pollicis, 98, (50)
superior, 108, (121)
anconeus, 95, (30)
internus, 95, (297)
lateralis, 95 (29a)
longus, 95, (29b)
posterior, 95, (29k)
antitragicus, 108, (127)
arytenoideus, in, (171)
attoUens auris 107, (no)
auricularis externus, 108, (124)
superior, 107, (no)

Muscles, biceps brachii, 95, (27)
femoris, loi, (57)
bi venter cervicis, 114, (198)
brachialis, 95, (28)
brachioradialis, 95, (31)
buccinator, 109, (136)
bulbocavernosus, 124, (233)
calcancometatarsalis, 107, (loi)
caninus, 109, (i3S)
capsularis, 103, (77)
caudoanalis, 124, (229)
caudocavernosus, 124, (232)
caudofemoralis, loi, (59)
caudorectalis, 124, (228)
caudo vaginalis, 124, (237)
cephalobrachialis, 93, (5)
cephalohumeralis, 93, (5)
ceratohyoideus, no, (135)
cervicofacialis, 92, (2)
clavobrachialis, 94, (19)
clavotrapezius, 93, (5)
cleidomastoideus, 93, (9)
coccygeus, 115, (218)
complexus, 114, (199)
compressor urethrae mem-

branaceae, 124, (234)
concheus externus, 108, (129)
constrictor cunni, 124, (235)
pharyngeus inferior, in, (164)

superior, in, (167)
coracobrachialis, 94, (25)
corrugator supercilii lateralis, 107,
(107)

medialis, 107, (105)
cricoarytenoideus lateralis, in,

(175)
posterior, in, (170)
cricothyreoideus, in, (169)
cruralis, 103, (78c)
cutaneous maximus, 92, (i)
deltoideus, 94, (18)
depressor conchae, 108, (116)
diaphragm, 115, (213)
digastric, no, (149)
ectopectoralis, 93, (14)
entopectoralis, 94, (15)

278

INDEX

Muscles, cpicranius, 107, (113)
epimeralis, 103, (77)
epitrochlcaris, 94, (26)
extensor antibrachii longus, 94,
(26)
brevis digitorum, 105, (92)

poUicis, 96, (39)
carpi radialis brevis, 96, (33)

longus, 96, (32)
carpi ulnaris, 96, (36)
caudac lateralis, 114, (193)

medialis, 114, (202)
communis digitorum, 96, (34)
digiti quinti proprius, 96, (35)
digitorum lateralis, 96, (35)

longus, 105, (90)
indicis proprius, 96, (37)
ossis metacarpi pollicis, 96, (38)
flexor brevis digiti quinti, 98, (54)
secundi, 98, (51)
brevis digitorum, 104, (81)

pollicis, 98, (49)
carpi radialis, 96, (41)

ulnaris, 97, (43)
caudae brevis, 115, (220)

longus, 115, (219)
longus digitorum, 104, (85)

hallucis, 104, (84)
perforans, 97, (45)
perforatus, 97, (44)
profundus digitorum, 97, (45)
sublimis digitorum, 97, (44)
frontoauricularis, 107, (108)
frontoscutularis, 108, (117)
gastrocnemius, 103, (79)
gemellus inferior, 102, (67)

superior, 102, (64)
genioglossus, no, (159)
geniohyoideus, no, (151)
glossoeppiglottis, in, (172)
glossopharyngeus, in, (163)
gluteus maximus, loi, (60)
medius, loi, (62)
minimus, 102, (65)
quartus, 103, (77)
gracilis, 102, (68)

Muscles, hclicis, 108, (125)
hyoeppiglottus, in, (173)
hyoglossus, no, (160)
iliocaudalis, 115, (216)
iliocostalis, 114, (194)
iliopsoas, 103, (76)
incisivi, 109, (138)
infraspinatus, 94, (21)
intercostales externi, 112, (184)

interni, 113, (185)
intermedius scuthlorum, 107,

(104)
interossei, 98, (51), 105, (95)
interspinalis, 114, (204)
intertransversarii, 114, (205)
ischiocavernosus, 124, (226)
jugulohyoideus, no, (152)
latissimus dorsi, 93, (10)
levator anguli oris, (caninus), 109,

(135)
ani, 115, (217)
auris longus, 107, (109)
claviculae, 93, (8)
labii superioris alaeque nasi,
109, (134)
proprius, 109,
(134b)
palpebrarum, 246
scapulae, 93, (12)
dorsalis, 93, (6)
ventralis, 93, (8)
scroti, 124, (230)
veli palatini, in, (162)
vulvae, 113, (235)
leva tores costarum, 115, (212)
longissimus capitis, 113, 114,(196)
cervicis, 113, (192)
dorsi, 113, (192)
longus atlantis, 114, (200)
capitis, 113, (187)
colli, 113, (188)
lumbricales, 97, (47), 105, (94)
mandibuloauricularis, 108, (126)
masseter, no, (154)
maxilloauricularis, 108, (126)
moustachier, 109, (138)

INDEX

279

Muscles, miiltifidus spinae, 114, (201)
myohyoideus, no, (150)
myrtiformis, 109, (137)
nasalis, in, (173)
obliquus abdominis extcrnus, 112,
(180)
internus, 112, (181)
capitis inferior, 114, (209)

superior, 113, (190)
superior, 115, (208)
obturator externus, 102, (73)

internus, 102, (66)
occipitofrontalis, 107, (113)
occipitoscapularis, 93, (6)
opponens digiti quinti (hand), 98,

(55),

(foot), 105, (98)
orbicularis oculi, 107, (106), 246

oris, 109, (132)
palpebrarum, 246
palmaris longus, 96, (42)
parameralis, loi, (59)
pectineus, 103, (75)
pectoantibrachialis, 93, (13)
pectoralis major, 93, (14)

minor, 94, (15)
pedis perforatus, 104, (81)
peroneus brevis, 104, (88)

longus, 104, (87)

tertius, 104, (89)
plantaris, 103, (80)
platysma, 92, (2)
popliteus, 104, (83)
pronator quadratus, 97, (46)

teres, 96, (40)
psoas minor, 115, (214)
pterygoideus externus, no, (157)

internus, no, (158)
pterygopharyngeus, in, (167)
pubiocaudalis, 115, (217)
pyriformis, 102, (63)
quadratus femoris, 102, (72)

labii inferioris, 109, (139)
superioris, 109, (134)

lumborum, 115, (215)

plantae, 105, (93)

Muscles, quadriceps femoris, 103, (78)
recti (eye), 247
rectocavernosus, 124, (231)
rectus abdominis, 112, (183)

capitis anterior major, 113,(187)
minor, 113, (189)

capitis lateralis, 114, (191)
posterior major, 114, (207)
medius, 115, (210)
minor, 115, (211)

femoris, 103, (78a)

inferior, 247

lateralis, 247

medialis, 247

superior, 247
retractor oculi, 247

penis, 124, (231)
rhomboideus, 93, (7)

capitis, 93, (6)
rotator auris, 108, (120)
sartorius, 102, (61)
scalenus, 112, (176)

anterior, 112, (176a)

medius, 112, (176a)

posterior, 112, (176b)
scaphocuneiformis, 107, (102)
scutuloauricularis inferior, 108,

(120)
semimembranous, 102, (70)
semispinalis capitis, 114, (199)

cervicis, 114, (203)
semitendinosus, 102, (69)
serratus anterior, 93, (n)

magnus, 93, (11)

posterior inferior, 112, (179)
superior, 112, (178)
soleus, 104, (82)
sphincter ani externus, 124, (224)

internus, 124, (225)
spinalis dorsi, 114, (197)
spinodeltoideus, 94, (17)
spinotrapezius, 92, (3)
splenius, 114, (195)
stapedius, 109, (131)
sternocleidomastoideus, 93, (9)
sternocostalis externus, 112, (177)

28o

INDEX

Muscles, stcrnocostalis intcrnus, 113,
(186)
sternohyoidcus, 109, (146)
sternomastoidcus, 109, (145)
sternothyrcoidcus, 109, (147)
styloglossus, no, (159)
stylohyoidcus, no, (148)
stylopharyngeus, in, (166)
submentalis, 108, (115)
subscapularis, 94, (23)
supcrcervicocutancus, 92, (2)
supinator, 96, ($S)

longus, 95, (31)
supraspinatus, 94, (20)
temporalis, no, (155)
tensor fasciae latae, loi, (56)

tympani, 109, (130)

veli palatini, in, (161)
tenuissimus, loi, (58)
teres major, 94, (24)

minor, 94, (22)
thyreoarytenoideus, in, (174)
thyreohyoideus, in, (168)
tibialis anterior, 105, (91)

posterior, 104, (86)
trachelomastoideus, 114, (106)
tragicus lateralis, 108, (119)

medialis, 108, (128)
transversus abdominis, 112, (182)

auriculae, 108, (123)

costarum, 112, (177)

menti, 109, (140)

pereni, 124, (227)

thoracis, 113, (186)
trapezius, 92, (3)
triangularis sterni, 113, (186)
triceps brachii, 95, (29)

surae (gastrocnemius and
soleus), 103
urethralis, 124, (238)
vastus intermedius, 103, (78d)

lateralis, 103, (78b)

medialis, 103, (78c)
xihumeralis, 94, (16)
zygomaticus major, 108, (114)

minor, 108, (133)

Myelenccphalon, 210

Nares, 47, 48, 191
Nasal bone, 50

process, 49
Nasolachrymal canal, 50

duct, 50

groove, 50
Navicular (scaphoid), 80
Naviculare pedis os (scaphoid bone), 80
Nerve cell, 228

fibre, 228
Nerves, arm, 234, 235

cranial, 232, 233
. leg, 237

motor, 231

peripheral, 231

plexuses, 234

sensory, 231

spinal, 233

sympathetic, 240
Nervous system, 14, 219
Nervus abducens, 232, 233

accessorius, 232, 233

acusticus, 232, 233

anterior crural, 239

auditory (acoustic), 232, 233

axillaris, 235

circumflexus, 235

cutaneous, external, 239
internal, 236

femoralis lateralis, 238
medialis, 238
posterior, 238

genitocrural, 237

genitofemoralis, 238

glossopharyngeus, 232, 2;^;^

glutei, 240

hypoglossus, 232, 233

iliohypogastric, 238

iliolingualis, 238

ischiadicus, 239

median, 235

musculocutaneus, 235

musculospiral, 235, 236

obturator, 239

occulomotorius, 232, 233

INDEX

281

Nervus olfactorius, 232, 233
opticus, 232, 233
patheticus (trochlear), 232, 233
peroneus profundus, 238

superficialis, 238
plantaris, internus, 23S
lateralis, 238
medialis, 238
pneumogastric (vagus), 232, 233
pudic, 240
radialis, 236

superficialis, 236
saphenus, 239
splanchnic, great, 242
subscapularis, 235
thoracicus anterior, 236
longus, 236
posterior, 236
tibialis, 238, 239
trigeminis, 232, 233
trochlearis, 232, 233
ulnaris, 237

vagus (pneumogastric), 232, 233
Neurone, 232

Nictitating membrane, 246
Nomenclature, 8
Notch, jugular, 45

inferior mandibular, 52
superior mandibular, 52
Nucleus, caudate, 222

lenticular, 222
Number of bones, 28, 29

Obturator foramen, 75, 76
Occipital bone, 45

condyle, 36

crest, 45
Odontoid process (dens), 56
Oleaginous gland, 250
Olecranon, 65

fossa, 65

process, 66
Olfactory bulb, 245

lobe, 211

organ, 245

tract, 214

Oligocene, 3
Omenta (um), 132
gastrocolic, 147

gastrohepatic, 147

greater, 132, 147

lesser, 136, 147
Optic chiasma, 212, 213

commissure, 212

foramen, 38

nerve, 232, 233

tract, 212, 213
Ora serrata, 249
Orbicularis palpebrarum, 246
Orbital cavity, 38

fissure, 38

fossa, 38

gland, 143

gyrus, 211

plate, 40, 49

process, 40
Orbitosphenoid, 45
Orders, 8
Ordovician, 3
Organ of corti, 252
Organs, 17

of body, 128
Ornithodelphia, 7
Os planum, 41
Ova of animals, 203
Ovary, 202

Pacinian corpuscle, 245
Pads of feet, 12, 26
Pain, sense organs of, 244
Palate, hard, 37
Palate, soft, 37
Palatine bone, 49

foramen, 38
Pancreas, 145

of Aselli, 183
Pancreatic bladders, 145

ducts, 145
Papillae of tongue, 129, 130
Parietal bone, 43

eminence, 43
Parotid duct, 143

282

INDEX

Parotid gland, 143

Patella, 77

Patellar ligament, 85

Pathetic (trochlear) nerve, 232, 233

Peduncles of cerebellum, 224

of cerebrum, 212
Pelvic arch, 75
bones, 75
Penis, 205
Pericardium, 150
Peripheral nervous system, 231
Perissodactyla, 8
Peritoneal cavity, 194
Peritoneum, 145
Permian, 3

Petrotympanic fissure, 37
Phalanges, 71, 81
Pharynx, 133
Phylogcny, 2

of horse, 67, 68, 69, 72
Physiology, i
Pia mater, 209
Pillars of fornix, 218

of fauces, 129
Pineal body, 221
Pinna, 249
Pinnipedia, 7
Pisiform, bone, 29, 68

ganglion, 220
Pituitary body (hypophysis), 212
Plantigrade, 73
Pleistocene, 3
Pleura, 194
Plexus, anterior gastric, 241

aortic, 241

brachial, 234

cardiac, 242

carotid, 241

celiac, 242

cervical, 234

hepatic, 242

inferior mesenteric, 242

lumbar, 237

lumbosacral, 237

posterior gastric, 241

Plexus, pulmonary, 241
renal, 242
sacral, 239
solar, 242
splenic, 242
superior mesenteric, 242

suprarenal, 242
Plica semilunaris, 246
Pliocene, 3
Poikilothermic, 5
Pons varolii, 224
Portal system, 12, 167
Postglenoid process, 44
Postorbital process, 42
Poupart's ligament, 201
Premaxillary bone, 48
Premolar teeth, 118
Preparation of bones, 15
Prepuce, 179

Preservation of material, 8, 233
Presphenoid bone, 37, 48
Primates, 7
Proboscidea, 8
Process, acromion, 64

alveolar, 131

angular, 50

anterior clinoid, 46

articular, 53

ciliary, 248

clinoid, anterior, 46

condyloid, 50

corocoid, 64

coronoid, 52

frontal, 51

hamular, 48

jugular, 45

malar, 49

mammillary, 58

mastoid, 44

nasal, 49

odontoid, 56, 57

orbital, 44

palatine, 44

posterior clinoid, 47

postglenoid, 44

INDEX

283

Process, postmandibular, 42

postorbital, 39, 51

pterygoid, 48

spinous, 53, 57

styliform, 66

transverse, 53, 57, 58

xiphoid, 61

zygomatic, 42
Promontory, 43
Prosencephalon, 210
Prostate gland, 206
Proterozoic, 3
Protocordata, 3
Prototheria, 7

Protuberance, external occipital, 36
Pterosaur, 6
Pterygoid bone, 45, 48

canal, 38

fossa, 37

process, 48
Pubis, 74
Pulmonary ligament, 195

plexus, 241
Puncta lachrymalia, 246
Pupil, 248
Psychology, i
Pyramids, anterior, 223

Quadrigemina, corpora, 219

Radial fossa, 66

notch, 66
Radius, 66

Rami communicantes, 227
Ramus of ischium, 75

of mandible, 51

of pubis, 75
Receptaculum chyli, 185, 186
Rectigrade, 73
Rectum, 139
Reflex action, 231
Reproductive system, 200, 203
Reptiles, 5

Respiratory system, 191
Restiform body, 223, 224
Retina, 248

Rhinencephalon, 213

Ribs, 61

Ridge, deltoid, 66

lambdoidal, 45

pectoral, 65, 66

supracondyloid, 65
Rodentia, 7

Rotatoria (pivot joint), 83
Ruminant, 134

stomach of, 147

Sacral canal, 71

foramena, 71

plexus, 212

vertebra, 58
Sacrum, 58
Sagittal crest, 36
Salivary glands, 142
Santorini, duct of, 145
Scala tympani, 241

vestibuli, 241
Scaphoid bone, 80
Scapholunar bone, 67
Scapula, 63
Scarpa's triangle, 164
Schneiderian membrane, 245
Sciatic nerve, 239

notch, 75
Sclera, 248
Sclerotic, 248
Scrotum, 204
Scutiform cartilage, 108
Sea cow, vertebrae of, 59
Sebaceous glands, 142
Selachian, 4
Sella turcica, 46
Semicircular canals, 251
Semilunar cartilages, 85

ganglion, 242, 243

notch, 66

tendon, 115

valve, 154
Sense organs, 244
Serous membrane, 146
Sesamoid bones, 28, 72, 81
Shoulder girdle, 63

284

INDEX

Sight, organs of, 246
Sigmoid cavity, 66
Silurian, 3
Sinus, frontal, 39

inferior petrosal, 170

lateral, 168

sphenoidal, 47

sui)erior longitudinal, 168
petrosal, 168
Sirenia, 8
Skeleton, 28

preparation of, 15
Skin, 25

sense-organs of, 244
Skull, ^i

Smell, organ of, 245
Soft palate, 129
Solar plexus, 243
Species, 8
Spermia, 205
Sphenoid bone, 45
Sphenopalatine foramen, 38
Spigelian lobe of liver, 144
Spinal column, 53

cord, 225

ganglia, 227

nerves, 206, 2$^
Spine, of ischium, 75

of scapula, 64

of tibia, 78
Spinous process, 53, 56, 67
Splanchnic nerves, 242
Spleen, 198
Splenic plexus, 242

Squamous portion of temporal bone, 42
Stapes, 240
Stenon's duct, (ductus parotideus

stcnonis), 143
Sternum, 61
Stria medullaris, 223
Stomach, 136, 140
Stylohyal, 51
Styloid process, 67
Stylomastoid foramen, 37
Sublingual gland, 143
Submaxillary gland, 143

Sulci of cerebellum, 211

of cerebrum, 224
Supracondyloid foramen, 65

ridge, 65
Supraoccipital bone, 43
Suprarenal (adrenal) gland, 188, 189
Sutures of skull, 35
Sweat glands, 26

Sympathetic nervous system, 240
Synarthroses, 83
Synovial membrane, 85
Systems, 17

Taenia thalami, 221

Tail bones, 58

Talus (astragalus), 29, 79

Tapetum, 248

Tarsal glands, 246

Tarsus, 29, 79

Taste, organs of, 245

Taxonomy, 2

Teeth, 130

mammalian, 133

milk, 133

permanent, 133
Telencephalon, 210
Teleosts, 5
Temporal bone, 41

fossa, 38
Tendo calcaneus (Achilles), 103
Tendon of Achilles, 103
Tentorium, 43
Testes, 204
Thalamus, 221
Thebesius, valve of, 153
Theromorph, 6
Thigh, bones of, 74

muscles of, 98
Thoracic, aorta, 154

cavity, 132

duct, 182, 185

ganglia, 241

vertebrae, 57
Thymus gland, 189
Thyreohyal, 52
Thyreoid cartilage, 52

INDEX

285

Thyreoid gland, 189
Tibia, 78

Tissues, 17, 18, 19, 20
Tongue, 129
Tonsils, 129
Tooth formula, 133

structure of, 130
Trabeculae carneae, 151
Trachea, 194
Tragus, 108

Trapezium (large multangular), 29, 68
Trapezoid (small multangular), 29, 69
Triangle, Scarpa's, 164
Triassic, 3

Tricuspid valve, 150
Triquetral (cuneiform) bone, 29, 68
Trochanter, great, 76

lesser, 76
Trochanteric fossa, 76
Trochlea tali, 79

humeri, 65
True ribs, 61
Truncus arteriosus, 1 73
Tuba auditiva (Eustachian tube), 37
Tuber cinereum, 212, 213
Tubercle, peroneal, 79

pubic, 75

of radius, 66

of ribs, 62
Tuberosity, great, 65

lesser, 65

of ischium, 75

of scapula, 64

tibia, 78
Tunica albuginia, 205

dartos, 104

fibrosa, 198

vaginalis communis, 204

proprius, 204
Turbinals, 49
Tj^mpanic bone, 35

bulla, 37, 42

cavity, 42

membrane, 240
Tympanohyal, 37

Ulna, 66

Unciform (hamate) bone, 29, 70

Unguiculata, 7

Ungulata, 7

evolution of, 67, 72
Unguligrade, 7s
Ureter, 199
Urethra, 200
Urogenital organs, 198

of mammals, 206
Uterine tubes, 201
Uterus, 201

Vagina, 201
Vagus nerve, 212, 213
Valsalva, sinuses of, 1 54
Valve of Vieussens, 214
\'alves of heart, 150

of veins, 165
Vas deferens, 205
\'asa efferentia testis, 205
Vascular system, 150

injection of, 9
Vater, ampulla of (opening of pancre-
atic and bile ducts, (145
Veins, 165

development of, 177
of lungs, 171

of trunk, head and neck, 165
Velum medullare superior, 214
inferior, 214
medullaris inferior, 223
Vena adrenolumbales, 166, 169
anonyma (innominate), 168
auricularis anterior, 169

posterior, 169
axillaris, 169
azygos, 167, 169
brachialis, 169
cardinalis, 179
cava, 165

cava anterior (precava), 165, 167,
169
cephalica, 165, 169
coronaria ventriculi, 165
facialis anterior, 168, 169

286

INDEX

\cna Cava, facialis posterior, i68, 169
gastroepiploica, 167
gastrolicnalis (gastrosplenic),

167
hepatica, 167
hypogastrica, 169
iliaca communis, 167, 196

externa, 167, 169

interna, 167, 169
iliolumbalis, 167, 169
innominata, 168
jugularis externa, 168, 169

interna, 168, 169
lumbaleSj 166
mammaria interna (sternal),

167, 169
mesenterica inferior, 167

superior, 167
ovarian, 167

pancreaticoduodenalis, 167
posterior, (postcava), 165, 169,

179
phrenica, 165
poplitea, 169
portae, 167
postcardinal, 177
postcava, 165

precardinal, 177
precava, 165
pulmonales, 171
renalis, 166, 169
sacralis media (caudal), 167, 169

saphena magna, 169
subcardinal, 177
subclavia, 168, 169
submentalis, 169
supracardinal, 177
thyreoideus inferior, 169
transversa scapulae, 169
umbilicalis, 177
vertebralis, 167, 168, 169
Ventricles of brain, 214

of heart, 152, 153
Vermiform appendix, 139, 147

Vermiform process, 224
Vermis, 224
Vertebrae, 53

caudal, 58

cervical, 54

lumbar, 58

number in mammals, 53, 59

of Orang, 59

of sea cow, 59

plan of, 53

thoracic, 53
Vertebral arch, 53

canal, 54

column, 53

foramen, 54
Vertebrarterial canal, 54
Vertebrata, 4
Vestibule of ear, 241
Vibrissae, 27
Vidian canal, 38
Villi, 142
Viscera, 134
Vital knot, 223
Vitreous body, 247, 249

humor, 247, 249
Vocal cords, false, 192

true, 192
Vomer, 49

Wharton's duct (submaxillary), 143

White matter of brain, 222

Willis, circle of, 158, 159

Winslow, foramen of, 145

Wirsung, duct of (larger pancreatic

duct), 14s
Wrist bones, 67

Xiphoid (ensiform) process, 61

Zygoma, 42

Zygomatic arch, 35
bones, 42
process, 42

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